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Picture of the productω-phase Transformation in Ti3Al2Mo alloy: ...
Omega-Phase Transformations in Ti3Al2Mo Alloy: A First Principles Approach
M. Sanati and R.C. Albers

The ω-phase appears as a metastable phase in several binary, ternary, and multicomponent alloys. While formation of this phase is studied extensively in Ti-Al-Nb and Ti-Al-V systems, it has not been investigated so widely in Ti-Al-Mo alloys. The aim of the present investigation is to study the displacive B2 to ω transformations in Ti3Al2Mo system by using first-principles calculations. We find that that atomic shuffles required for the transformation in Ti3Al2Mo are about half of the Ti3Al2Nb alloy. We calculate heat of formation for several compounds to understand the bonding and hybridization between the atoms and the reason behind the differences between these to systems. It is found that Ti-Nb bond is weaker than Ti-Mo while Nb-Al is much stronger than Mo-Al. The stability of B2 phase against ω-type atomic displacement is a competition between these bonds. Also by extending our calculations to finite temperature, we show that the addition of Mo will extend the ω-phase stability to higher temperature compared to Ti3Al2Nb system.

Publisher: TMS
Product Format: PDF
Pages: 429-433
Date Published: January 1, 2010


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10-7452-429
Picture of the product3D Reconstruction of Coarse Dendritic Microstructures ...
3D Reconstruction of Coarse Dendritic Microstructures during the Solidification of Al-Cu Alloys
D. Ruvalcaba, D. G. Eskin, L. Katgerman

Defects that develop during solidification of aluminum alloys (e.g. hot tearing) depend, among other things (e.g. casting process), on the morphological evolution of microstructure. Quenching (i.e. "freezing") of the microstructure during solidification may be used as a technique for studying the structure development of aluminum alloys, however the metallographic examination of the as-quenched structure shows an overestimation of the solid fraction as related to the temperature of quenching. In the present study, the 3D microstructure reconstruction of asquenched samples revealed features that showed a coalescence of the finer solid regions formed upon quenching, which might cause the overestimation of the solid fraction as compared to the lever rule and Scheil approximation. The paper presents observations of the 3D microstructure development during solidification of an Al-7 wt% Cu alloy by using the quenching technique and serial sectioning for stacking and 3D reconstruction. The identification and removal of structure instabilities may help in reconstructing the microstructure that develops during solidification.

A collection of papers from the 2007 TMS Annual Meeting & Exhibition held in Orlando, Florida, February 25–March 1, 2007.



Publisher: TMS
Product Format: PDF
Pages: 1-9
Date Published: May 1, 2007


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07-6813-1
Picture of the product3D Reconstruction of Ni4Ti3 Precipitates in a Ni-Ti...
3D Reconstruction of Ni4Ti3 Precipitates in a Ni-Ti Alloy by FIB/SEM
Shanshan Cao, Wim Tirry, Wouter Van Den Broek and Dominique Schryvers

Ni4Ti3 precipitates play an important role in the shape memory and superelastic behaviour of thermo-mechanically treated Ni-Ti material. The 3D morphology and distribution of such precipitates with lenticular shape and rhombohedral atomic structure in the austenitic B2 matrix of a binary Ni-rich Ni-Ti alloy has been elucidated via a slice & view procedure in a Dual-Beam FIB/SEM system. With the sequence of cross-section SE images obtained from the SEM, a 3D reconstruction has been achieved after proper alignment and image processing, from which both qualitative and quantitative analysis can be performed. Careful imaging is needed to ensure that all variants of the precipitates are observed with equal probability, regardless sample orientation. Moreover, due to the weak contrast of the precipitates, proper imaging conditions need to be selected to allow for semi-automated image treatment. Finally, in the case of an experiment with a 50nm slicing step, a volume ratio of 5.6% for the Ni4Ti3 precipitates could be calculated, summed over all variants, which yields a net composition of Ni50.62Ti49.38 for the matrix, leading to an increase of 68 degrees for the martensitic start temperature Ms. Also, the expected relative orientation of the different variants of the precipitates could be confirmed. Other quantitative measures on the distribution of the precipitates are obtained as well.

Publisher: TMS
Product Format: PDF
Pages: 561-565
Date Published: January 1, 2010


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10-7452-561
Picture of the product3DAP Study of Alloy Element Effects on the Tempering of Stee
3DAP Study of Alloy Element Effects on the Tempering of Steel
Chen Zhu, Xiangyuan Xiong, Alfred Cerezo, George Krauss, and George D.W. Smith

It is well known that the addition of alloy elements such as Si, Cr, Mn, Ni and Mo increases the resistance of carbon-containing martensitic steels to softening during tempering treatments. In the case of high silicon steels, the rate-controlling process has previously been identified as being the rejection of this element during the growth and coarsening of cementite. However, the mechanisms operating in the case of other alloy elements remain obscure. In the present work, we are studying the tempering of an engineering steel, AISI / SAE 4340 (Fe- 1.83at%C - 0.69 Mn - 0.83 Cr - 1.67 Ni - 0.51 Si - 0.15 Mo) in the temperature range 250 °C – 600 °C. We are using 3-D atom probe techniques to map the redistribution of all major alloying elements between ferrite and carbide phases as a function of temperature and time. A progress report on this work will be presented. It is remarkable that significant retardation of softening rate is observed at tempering temperatures as low as 300 °C, where substitutional solute redistribution is barely detectable, even by the most sophisticated 3DAP data analysis techniques. Possible explanations for the observed effects on tempering kinetics will be discussed.

Publisher: TMS
Product Format: PDF
Pages: 17-23
Date Published: May 1, 2007


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07-6783-17
Picture of the product4H-SiC Based Neutron Flux Monitors in Very High...
4H-SiC Based Neutron Flux Monitors in Very High Temperature Nuclear Reactors
B. Khorsandi, W. Windl, T.E. Blue, W. Luo, J. Kulisek, M. Reisi-Fard, and V. Krishnan

Next-generation high-temperature reactor types will possibly operate at temperatures up to 1000 °C. In order to monitor the neutron flux in this environment, a new type of diode neutron detector is currently under development based on the 4H polytype of silicon carbide. An important problem in this context is the long-time reliability of the diodes with respect to the continuous irradiation and high temperatures in next-generation reactors. Using multiscale modeling, we will study the effects of continuous irradiation on the electrical properties of the diode by combining existing Monte Carlo and binary-collision approximation based codes (MCNP5, MARLOWE) for neutron/solid interactions and damage-cascade creation with a new ab-initio assisted kinetic-Monte Carlo code for simulation of the annealing effects and atomic-level electronic-structure based modeling for the charge transport.

Keywords: MCNP, TRIM, Multiscale Modeling, High Temperature Nuclear Reactors

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0603-23
Picture of the productA 6-D Structural Model for the Icosahedral (Al, Si)-Mn
A 6-D Structural Model for the Icosahedral (A1,Si)-Mn Quasicrystal
J. W. Cahn and D. Gratias and and B. Mozer

A 6-dimensional (6-D) periodic model is proposed for the Al-Mn-Si icosahedral quasiperiodic crystal. The model results from an embedding of the periodic cubic a structure in 6-D. In the Janner-Janssen-Bak description, it consists of three concentric spherical shells of respectively Mn, Al and Al aligned in perpendicular space around the lattice nodes and two additional shells of Al around the body centers. This model is shown to match the X-ray powder diffraction data with a satisfactory residual R-factor of 0.128.

Publisher: TMS
Product Format: PDF
Pages: 483-493
Date Published: September 1, 1998


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01-416X-483
Picture of the productA Coherency Strain Model for Hexagonal-Close-Packed Alloys
A Coherency Strain Model for Hexagonal-Close-Packed Alloys
C.N. Varney, G.L.W. Hart, and C. Wolverton

KEY WORDS Computer Applications and Process Control and Modeling and Simulation

Encouraged by the success of first-principles cluster expansion methods for large-scale modeling of cubic alloys, we are developing a mixed-space cluster expansion approach for hexagonal-close-packed alloys. Here we discuss an explicit strain model, an essential component of cluster expansion models for modeling precipitate formation. We illustrate the method for magnesium alloys containing calcium and yttrium, two common additives in magnesium alloys.

This paper is included in TMS Letters,Vol. 1:2 (2004).

Publisher: TMS
Product Format: PDF
Pages: 35-36
Date Published: February 1, 2004


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LET-0402-35
Picture of the productA Comparative Study of Numerical Methods and Computational T
A Comparative Study of numerical Methods and Computational Tools for Phase Field Equations of Solidification
Zhiheng Huang and Paul P. Conway

A Partial Differential Equation (PDE) or coupled PDEs need to be solved in phase field microstructural modelling. Finite difference discretization in space is commonly used to solve such equations numerically. Spectral methods can also solve PDEs to a high accuracy on a simple domain. However, those two methods should be treated with care when the domain of interest is irregular. In such cases, the finite volume method or finite element method is a natural alternative. A numerical algorithm implemented in a basic computer language such as C is a computationally efficient method. However, some high-level computing environments or software packages provide the advantages of easy implementation and flexibilities in visualization. This paper provides a comparative study of that uses different numerical methods and computational tools to solve coupled phase field equations of solidification. The methodologies presented in this paper can be equally applied to other PDEs in phase field modelling.

Publisher: TMS
Product Format: PDF
Pages: 1-9
Date Published: May 1, 2007


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07-6677-1
Picture of the productA Comparison of Cyanide and Thiosulfate Leaching for the Rec
A Comparison of Cyanide and Thiosulfate Leaching for the Recovery of Gold from a Copper Containing Ore
X. Dai, C.K. Chu, M. Jeffrey, and P. Breuer

One of the biggest challenges for the gold industry in the 21st century is the presence of copper in gold containing ore bodies. This is because copper consumes large quantities of cyanide. In addition, copper cyanide species are more stable than free cyanide, and hence are problematic in events of tailings spillage. The present paper compares cyanide and thiosulfate leaching for the recovery of gold from a copper containing ore. For cyanide leaching, the extraction of gold using copper cyanide complexes instead of free cyanide was tested in the presence and absence of added ammonia. For the thiosulfate leaching, the effect of the minerals present in the ore on the solution potential and thiosulfate consumption are illustrated.

Publisher: TMS
Product Format: PDF
Pages: 123-138
Date Published: August 1, 2003


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03-5549-123
Picture of the productA Comparison of Surfactant Aggregation Transition Concentrat
A Comparison of Surfactant Aggregation Transition Concentration Determined Using Electrochemical Quartz Crystal Microbalance Tests, Surface Tension Measurements, Corrosion Inhibition Tests, and Theoretical Methods
D.Y. Ryu and M.L. Free

KEY WORDS: Surface Modification and Coating and Electrometallurgy

The surfactant aggregation transition concentration (atc) is the concentration associated with the transition from surfactant monomers to aggregates such as micelles in solution or from near monolayer to multilayer coverage on surfaces. Usually the atc values for solution and surface behavior are similar although they are usually not identical due to surface energy issues associated with interfacial adsorption. Atc values can be determined by various methods such as Electrochemical Quartz Crystal Microbalance (EQCM), surface tension, and corrosion inhibition tests as well as theoretical methods. This paper discusses various approaches for determining the atc values as well as the factors that affect atc values.

This paper is included in TMS Letters,Vol. 1:3 (2004).

Publisher: TMS
Product Format: PDF
Pages: 49-50
Date Published: March 1, 2004


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LET-0403-49
Picture of the productA Comprehensive Copper Stockpile Leach Model: Background
A Comprehensive Copper Stockpile Leach Model: Background and Model Formulation
C.R. Bennet, M. Cross, T.N. Croft, J.L. Uhrie, C.R. Green, and J.E. Gebhardt

The first phase in the design, development and implementation of a comprehensive computational model of a copper stockpile leach process is presented. The model accounts for transport phenomena through the stockpile, reaction kinetics for the important mineral species, oxygen and bacterial effects on the leach reactions, plus heat, energy and acid balances for the overall leach process. The paper describes the formulation of the leach process model and its implementation in PHYSICA+, a computational fluid dynamic (CFD) software environment. The model draws on a number of phenomena to represent the competing physical and chemical features active in the process model. The phenomena are essentially represented by a threephase (solid-liquid-gas) multi-component transport system; novel algorithms and procedures are required to solve the model equations, including a methodology for dealing with multiple chemical species with different reaction rates in ore represented by multiple particle size fractions. Some initial validation results and application simulations are shown to illustrate the potential of the model.

Publisher: TMS
Product Format: PDF
Pages: 315-328
Date Published: August 1, 2003


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03-5549-315
Picture of the productA cyclic model for thermomechanical behavior of shape...
A Cyclic Model for Thermomechanical Behavior of Shape Memory Alloys
L. Saint-Sulpice, S. Chirani, and S. Calloch

This study concerns a macroscopic approach to model the thermomechanical behavior of Shape Memory Alloys (SMA) under cyclic loading. The model has been developed first for the superelasticity and then extended to assisted two way memory effect. In this model, a particular attention has been paid to the description of the evolution of residual strain with number of cycles after experimental verifications. The originalities of the model are, on the one hand, the definition of a particular elasticity domain when the material is in a two phased state and, on the other hand, an ad hoc kinetic of transformation strain taking into account a residual strain evolution based on the jammed martensite.

Publisher: TMS
Product Format: PDF
Pages: 473-480
Date Published: January 1, 2010


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10-7452-473
Picture of the productA Dislocation Model of Parent-Martensite Interfaces
A Dislocation Model of Parent-Martensite Interfaces
R.C. Pond, X. Ma, and J.P. Hirth

Interfaces separating parent and product phases are modelled using dislocation theory. Glissile interfaces are partially coherent structures; a network of dislocations and disconnections accommodates the coherency strains, and lateral motion of the disconnections across the interface effects the transformation. The short and long-range distortion fields of static interfaces are defined. The long-range strains disappear for ideal solutions, but small rotations may persist, depending on the constraints imposed. Plastic transformation strains are expressed as the combined strains due to the motion of disconnections and dislocations.

The topological model of {575} lath martensite habits formed in ferrous alloys are described, and shown to be consistent with experimental observations. A range of solutions is found with orientation relationships varying from Nishiyama-Wasserman to Kurdjumov-Sachs; quantifiable degrees of sessile constraint and residual coherency strain arise for non-ideal solutions.

Publisher: TMS
Product Format: PDF
Pages: 107-114
Date Published: January 1, 2010


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10-7452-107
Picture of the productA Lodel of the Cathode Dynamics in Electric Field-Enhanced S
A Model of the Cathode Dynamics in Electric Field-Enhanced Smelting and Refining of Steel
D. Dussault and A. Powell

Electric Field-Enhanced Smelting and Refining is a process for driving the reaction between carbon in hot metal and iron oxide in slag, for example, in a steelmaking reactor. This process involves inserting electrodes into the slag and metal phases, such that the overall reaction FeO + C –> Fe + CO is separated into two half-cell reactions: Fe2+ + 2e –> Fe at the cathode in the slag, and C + O2– –> CO + 2e at the anodic slag-metal interface. Without the electrodes, the reaction is very slow, but with electrodes, the additional surface area available to the ferrous ions for reduction accelerates the reaction even without any applied bias. When a bias is applied to the electrodes, the electric field across the slag further accelerates the overall reaction.

Publisher: TMS
Product Format: PDF
Pages: 249-250
Date Published: February 1, 2002


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01-5131-249
Picture of the productA Marker Chain Front Tracking Method for Modelling Meniscus
A Marker Chain Front Tracking Method for Modelling Meniscus Dynamics in the Al Ingot Casting Process
F. Iversen, J.A. Bakken and S.T. Johansen

A new marker chain front tracking method is used for modelling the meniscus movement during DC casting of aluminium ingots. Modifications have been made to an earlier method developed by Popinet and Zaleski [12] to adapt the model for simulations of meniscus dynamics in the casting process. Initial casting simulations show that wetting conditions in the mould greatly influence the meniscus stability. Controlling the wetting conditions seems to be important for improving the cast ingot surface quality.

Publisher: TMS
Product Format: PDF
Pages: 323-334
Date Published: February 1, 2002


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01-5131-323
Picture of the productA Mathematical Model for the Control of Metallurgical Proper
A Mathematical Model for the Control of Metallurgical Properties of the Product Sinter
N. Dube and E.F. Vegman

In the practice of conventional sintering, production is always afflicted with the problem of being unable to get a uniform quality of produced sinter in the bed. Invariably the top layer of the sinter cake is composed of weak but highly sinter, while the bottom layer is over-fused, forming a sinter that is very strong but less reducible. These symptoms point to a variable distribution of the heat balance in the process of sintering which results in a deficit of heat in the top layers of the sinter bed and an excess of heat in the bottom layers, due to an increasing input of regenerated heat in the heat balance down the bed. This causes losses in the productivities of the sinter machine and the blast furnace.

The current work was designed to improve on the solution to the above problem through the establishment of a more accurate combustion zone heat balance of the sintering process. This development is mostly on the method of determining the regenerated heat input in the overall heat balance. Previous methods were based on the assumption that the width and the velocity of the combustion zone remain constant through out its whole life, which is not the case since tests have shown that both its width and velocity increase as the combustion zone moves down the bed. In this work, these factors have been taken into account. Tests and calculations using the model were carried out for haematite and limonitic ores. The high sensitivity of the model to changes in the sinter mix composition and sintering conditions was demonstrated. The results present the following prospects:
• The minimum theoretically possible coke breeze consumption during the sintering of any type of iron ore fines, under any sintering conditions, can be established.
• The model can be used to control the metallurgical quality of the sinter in any point in the sinter bed since calculation data includes desired basicity, combustion zone temperature and FeO content in the sinter produced.

Publisher: TMS
Product Format: PDF
Pages: 251-262
Date Published: February 1, 2002


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01-5131-251
Picture of the productA Mechanism for Fatigue Crack Initiation in Pure Metal
A Mechanism for Fatigue Crack Initiation in Pure Metal
T. Zhai

In this paper, a model for fatigue crack initiation is proposed, based on the experimental observation that there is always a net irreversible slip in one direction of the active slip in a metallic material. Such irreversible slip leads to a local shear stress which encourages the dislocations with a Burgers vector of opposite sign to slip out of the surface minimize the net irreversible slip effect. Continuous slipping out of the surface by dislocations from two adjacent positive and negative sources could lead to crack nucleation on the surface. This net irreversible slip model appears to be also able to explain other observed fatigue surface damage such as formation of macrobands, extrusions and intrusions in Al, Cu, Cu-Al alloy and Mg single crystals. It may form the basis to build up a quantitative model for fatigue crack initiation in metallic materials.

Publisher: TMS
Product Format: PDF
Pages: 91-98
Date Published: March 1, 2002


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03-5441-91
Picture of the productA Mechanistic Based Study of Fatigue Crack Propagation in th
A Mechanistic Based Study of Fatigue Crack Propagation in the Single Crystal Nickel Base Superalloy CMSX-2
S.D. Antolovich and B.F. Antolovich

Creep considerations have been a driving force for the introduction of single crystal nickel base superalloy components into gas turbine engines. Nonetheless, fatigue considerations necessitate accurate fatigue crace propagation (FCP) modelling to prevent costly failures. FCP in single crystals is characterized by non-self-similar crack growth and for nickel base superalloys the appearance of multiple distinct fracture morphologies. Therefore, traditional FCP rate modelling using DKI as a correlating factor for crack growth rates is questionable. FCP rate tests were conducted using CMSX-2 at room temperature and 973K in air and vacuum with two different crystallographic orientations. It was found that all cracking was associated with two distinct morphologies on the fracture surface; one in which the g precipitates where sheared and one in which they were avoided. Transmission electron microscopy (TEM) confirmed that two different mechanisms were opereating; one in which the dislocations sheared the precipitates and one in which they bypassed the precipitates. A finite element analysis (FEA) was performed to predict the stresses and strains ahead of the crack tip for each tested condition. The combination of FEA and TEM in conjunction with scanning electron microscopy (SEM) observations suggests that the non-self-similar crack growth and distinct morphologies are controlled by the state of stress. High resolved shear stresses in the direction of the Burger's vector along with low normal stresses on the cube faces of the g precipitates produced crystallographic crack growth while low resolved shear stresses and high normal stresses produced g avoidance crack growth. This fundamental understanding of the crack growth mechanisms will assist in more accurately modelling FCP rates in single crystal nickel base superalloys.

Publisher: TMS
Product Format: PDF
Pages: 9-23
Date Published: March 1, 2002


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03-5441-9
Picture of the productA Metallic Phase with Long-Ranged Orientational Order and No
Metallic Phase with Long-Range Orientational Order and No Translational Symmetry
D. Shechtman, I. Blech, D. Gratias and J. W. Cahn

We have observed a metallic solid (Al-14 at.%Mn) with long-range orientation order, but with icosahedral point group symmetry, which is inconsistent with lattice translations. Its diffraction spots are as sharp as those of crystals but cannot be indexed to any Bravais lattice. The solid is metastable and forms from the melt by a first-order transition.

Publisher: TMS
Product Format: PDF
Pages: 429-435
Date Published: September 1, 1998


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01-416X-429
Picture of the productA Micro-Indentation Method for Assessment of TBC Bond...
A Micro-Indentation Method for Assessment of TBC Bond Coat Systems
C. Feng, M. Alvin, and B. S.-J. Kang

Under elevated temperatures, the presence of high thermal stresses along or within thermal barrier coatings (TBCs) can lead to the development of creep cavities and wedge cracks which can ultimately form microcracks and result in interfacial debonding in the TBC bond coat region. Defects detection on the subsurface TBC layers has shown some progress by using laser scattering and other non-destructive testing (NDT) methods. However, the difficulty of determining interfacial debonding and degradation assessment of the TBC remains a significant hurdle to overcome due to the TBC’s complex multi-layer structure, and frequently rough surface morphology. The TBC has high attenuation, high porosity, and many interfaces of different materials, which are the challenges that need to be overcome by the NDT techniques. Based on our recent research development of a Transparent Indenter Measurement (TIM) method, we have further developed a simplified micro-indentation technique for mechanical property degradation measurement and debonding/spallation detection of TBC bond coat in this research effort. NETL bond-coated coupons were subjected to cumulative rapid thermal cycling, and after every 100 high temperature thermal cycles, micro-indentation tests were conducted on bond-coat superalloy and single crystal coupons. Preliminary test results showed that the measured surface stiffness responses of the NETL bond coat decreased with exposure to continued thermal cycling. Currently these data are being correlated with microstructural analyses to address potential degradation and/or spalling of the applied NETL bond coat.

Keywords: TBC, bond coat, micro-indentation, multiple partial unloading

Publisher: Materials Science and Technology Conference (MS&T) 2007
Product Format: PDF
Date Published: September 16, 2007


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08-0703-1
Picture of the productA Micromechanical Continuum Model for the Tensile Behavior
A Micromechanical Continuum Model for the Tensile Behavior of Shape Memory Metal Nanowire
Wuwei Liang and Min Zhou

A novel shape memory behavior is discovered recently in single-crystalline FCC nanowires of Cu, Ni, and Au with lateral dimensions below 5 nm. Under proper thermomechanical conditions, these wires can recover elongations up to 50%. This phenomenon only exists at the nanoscale and is associated with reversible lattice reorientations within the FCC lattice structure driven by surface stresses. This paper presents a mechanism-based micromechanical continuum model for the tensile behavior. This model uses a decomposition of the lattice reorientation process into a reversible, smooth transition between a series of phase-equilibrium states and a superimposed irreversible, dissipative propagation of a twin boundary. The reversible part is associated with strain energy functions with multiple local minima and quantifies the energy conversion process between the twinning phases. The irreversible part is due to the ruggedness of the strain energy landscape associated with dislocation nucleation, gliding, and annihilation and characterizes the dissipation during the transformation. This model captures all major characteristics of the behavior, quantifies the size and temperature effects, and yields results which are in excellent agreement with data from molecular dynamics simulations.

Publisher: TMS
Product Format: PDF
Pages: 11-21
Date Published: May 1, 2007


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07-6882-11
Picture of the productA Microscopic Theory of Domain Wall Motion and Its Experimen
A Microscopic Theory for Domain Wall Motion and Its Experimental Verification in Fe-A1 Alloy Domain Growth Kinetics
J. W. Cahn and S. M. Allen

A microscopic theory for curved antiphase domain wall motion in ordered structures leads to a prediction that velocity is proportional to mean curvature. Unlike previous models, the velocity is not proportional to domain wall free energy. Experimental results on domain growth in ordered FeAl alloys over a range of temperatures, times and compositions, are consistent with the theory. In the vicinity of the critical temperature where domain wall free energy tends to zero, domain growth is not slowed.

Publisher: TMS
Product Format: PDF
Pages: 369-376
Date Published: September 1, 1998


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01-416X-369
Picture of the productA Microstructural Examination of Aluminum Alloys Subjected t
A Microstructural Examination of Aluminum Alloys Subjected to Incremental Forming
A. Krause, W.T. Donlon, A.J. Gillard, and S. Golovashchenko

Improvements in formability of certain aluminum alloys is required for utilization by the automotive industry for complex shaped body panels to reduce vehicle weight. One possible approach to increase formability is through incremental forming; a process of deforming the aluminum sheet in separate steps, with the sheet being subjected to a quick recovery heat treatment between each forming step, in order to partially undo the effects of work hardening. This process can significantly increase the total amount of deformation before fracture. The purpose of this work was to determine if the structural mechanism responsible for the partial recovery of both aging and non-aging aluminum alloys could be determined. The microstructure was examined through both optical and transmission electron microscopy for alloys subjected to a variety of temperatures and deformations.

Publisher: TMS
Product Format: PDF
Pages: 77-86
Date Published: June 1, 2007


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06-6110-77
Picture of the productA Model for Calculating the Lankford Value in Sheet Steels
A Model for Calculating the Lankford Value in Sheet Steels
S. Jiao, C.I. Garcia and A.J. DeArdo

A practical model based on the Hill analysis has been developed to calculate the Lankford value of interstitial free (IF) steels and its distribution in different rolling directions, by considering only a few selected texture components. The Texture Intensity Ratio (TIR), i.e. (111)/(100), was used in the model to describe texture. By using the new TIR parameter, the texture-based prediction models can be used more easily to predict the Lankford value in a rather straightforward way.

Publisher: TMS
Product Format: PDF
Pages: 605-612
Date Published: February 1, 2002


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01-5131-605
Picture of the productA Model to Predict the Damping Characteristics of Piezoelect
A Model to Predict the Damping Characteristics of Piezoelectric-Reinforced Metal Matrix Composites
A.C. Goff, A.O. Aning, and S.L. Kampe

KEY WORDS: Composites and Modeling and Simulation

A numerical model based on the Eshelby equivalent inclusion method has been developed as a means to gauge the energy absorption (damping) capability of piezoelectric-reinforced metal matrix composites. The model computes the joule heating generated within a variety of metallic matrices as a consequence of the mechanical excitation of various randomly dispersed piezoelectric reinforcement formulations. The model predicts that enhanced damping performance by such a mechanism would, in general, be realized for highly conductive metallic matrices containing reinforcements with high piezoelectric capability.

This paper is included in TMS Letters,Vol. 1:3 (2004).

Publisher: TMS
Product Format: PDF
Pages: 59-60
Date Published: March 1, 2004


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LET-0403-59
Picture of the productA New Continuous Manufacturing Technology for Nanoparticles
A New Continuous Manufacturing Technology for Nanoparticles
Christian Wögerer, Georg Waldner, Nils Stelzer, Heinz Dobesberger

The most important challenge is, besides development of new particles and materials based on “Nano”, to create new “Production” methods for a controlled mass production of Nanoparticles. Therefore ARC has recently started the operation of an advanced HPMN- trial plant that enables the synthesis of various types of nanoscaled particles. The goal is establishing a proven method for the production of nanoparticles for industries. The paper shows the state of the art of various production methods with its advantages and disadvantages and compares these technologies to the HPMN reactor. The HPMN reactor is a continuous production method for Nanoparticles with the Possibility of functionalsazion and aftertreatment in one step and he will open the door for the Industries to a cost efficient mass production of functionalized Nanoparticles and Nanoproducts. The HPMN-reactor combines the flexibility of precipitation with the possibilities of controlling the particle characteristics and the ability of continuous processing.

Publisher: TMS
Product Format: PDF
Pages: 19-28
Date Published: May 1, 2007


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07-6912-19
Picture of the productA New DC-DC Converter for Fuel Cell Powered Distributed...
A New DC-DC Converter for Fuel Cell Powered Distributed Power Generation Systems
Rahul Sharma and Hongwei Gao

Fuel cell powered distributed power generation systems are considered attractive because of their various advantages, such as high efficiency, low pollution, and low noise. A DC-DC converter having a high turns ratio transformer is needed in such a system, to boost the low voltage of the fuel cell to a high level, to enable the DC-AC conversion and to provide isolation. The high turns ratio of the transformer causes a high leakage inductance, and therefore, reduces efficiency, and increases difficulty in control of the DC-DC converter. In this paper a new DC-DC converter for fuel cell powered distributed power generation systems is propose. The proposed converter uses the leakage inductance for energy conversion, which not only reduces the problems of low efficiency and difficulty of control, caused by leakage inductance, but also eliminates the need for a separate inductor. Lack of a separate inductor helps reduce the cost of the DC-DC converter. Also, soft switching is employed to reduce the switching losses. Consequently, the proposed DC-DC converter has low cost and high efficiency. Simulation and experimental results are presented to verify the proposed DC-DC converter.

Keywords: DC-DC Converter, Fuel Cell, SOFC

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0603-21
Picture of the productA New Free Surface Prediction Technique for Finite Element S
A New Free Surface Prediction Technique for Finite Element Simulation of Shape Rolling
H.J. Kim, T.H. Kim, W.Y. Choo, and S.M. Hwang

A new, steady-state process model is presented for the prediction of the deformation of the workpiece in shape rolling. Described are a three-dimensional finite element model for the analysis of plastic deformation, a new streamline tracing scheme, and the schemes for free surface convergence, including those for free surface prediction and correction. The process model is then applied to multi-pass rolling of a variety of commercial parts, to demonstrate the capability to deal with rolling of a complex-shaped part. Also investigated is the model's prediction accuracy, through comparison with the measurement.

Publisher: TMS
Product Format: PDF
Pages: 377-384
Date Published: September 1, 2004


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04-0022-377
Picture of the productA New Generation of Tool Steels for Shaping AHSS and UHSS
A New Generation of Tool Steels for Shaping AHSS and UHSS
B. Casas, D. Marco, and I. Valls

Advanced high strength steels (AHSS) and ultra high strength steels (UHSS) exhibit a unique combination of high strength, excellent energy absorption during deformation and strain hardening. These outstanding properties have permitted their increasing use in automobile industry to diminish vehicle weight and thereby fuel consumption while improving crash performance. However, forming processes of such high strength materials involve severe difficulties due to the high load requirements that increase to a great extent the tool demands in terms of toughness and hardness properties. In this work, a new generation of tool steels are developed in order to reduce these drawbacks. In doing so, a detailed characterization of tool steels used in shaping processes of AHSS and UHSS has been assessed to distinguish main failure mechanisms and tribomechanical functionality of different carbides, nitrides, borides and oxides. The microstructural optimisation, in terms of matrix composition as well as nature, morphology, size and distribution of second phase particles, has been crucial in the development of a new generation of tool steels with exceptional combination of properties which make them the best candidates for shaping high strength materials as AHSS and UHSS.

Keywords: Cold work tool steels, shaping AHSS and UHSS, microstructural optimization

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0601-14
Picture of the productA New Mechanism for Superplasticity
A New Mechanism for Superplasticity
J.C.M. Li

This paper is dedicated to Dr. Bhakta Rath for his important contributions to the science and technology of interfaces. I cherish the good old days at the Edger C. Bain Laboroatory for Fundamental Research at the U. S. Steel Research Center where Bhakta, Bill Hu and myself often discussed the structure of grain boundaries and interfaces. We made a lot of progress in the few short years we were together under the leadership of Dr. Lawrence S. Darken.

Publisher: TMS
Product Format: PDF
Pages: 155-169
Date Published: February 1, 2002


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01-5204-155
Picture of the productA New Method for Modeling 3D Constitutive Relation...
A New Method for Modeling 3D Constitutive Relation Based on Orientational Components
Cheng Wei

A new method for modeling 3D constitutive relation based on orientational components was investigated. Improved representations of stress/strain vectors and of Euler angles as orientational parameters were proposed. Some principles which should be complied with by mechanical units were introduced. According to these, four basic units for simulating primary mechanical properties of material at local orientations were introduced. As a new concept, orientational component, used to simulating micro-mechanical properties of materials at local orientation, was presented by superposing basic units. Then a frame composed of orientational components was created, of which the ratio of component at each orientation was quantified by orientation density function. The integral representation for building macroscopic stiffness matrix was derived. Moreover, the sufficiency of the units, the general forms of components, the universality of the orientational constitutive relations, and the aspects of the further research, were discussed.

Keywords: constitutive relation, orientation density functions, unit, component

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0604-5
Picture of the productA New Polymorph of Zinc Oxide in Nanowires under Tensile Lad
A New Polymorph of Zinc Oxide in Nanowires under Tensile Loading
Ambarish J. Kulkarni, Min Zhou, Kanoknan Sarasamak, and Sukit Limpijumnong

We report a previously unknown 5-fold coordinated polymorph of ZnO with a graphitic (P63/mmc) structure which results from a reversible phase transformation from the wurtzite (P63mc) structure. Molecular dynamics simulations show that this transformation occurs in []-oriented nanowires under uniaxial tensile loading and is associated with recoverable strains up to 15% and a low level of hysteretic energy dissipation (0.16 J/m3) per transformation cycle. First principles calculations show that this new polymorph (herein denoted as the HX state) corresponds to a distinct minimum on the enthalpy surfaces of ZnO under the conditions of the uniaxial tensile stress considered. The density functional theory (DFT) calculations also reveal a relatively low transformation energy barrier of ~0.05 eV, providing an explanation for the small size of the hysteresis loop in the stress-strain relation and the low level of energy dissipation associated with the loading-unloading transformation cycle. The slender one-dimensional shape of the nanowires and the uniaxial nature of the tensile loading along the [] crystalline direction combine to provide the necessary driving force for this transformation which occurs through atomic shifts toward higher coordination and ionicity.

Publisher: TMS
Product Format: PDF
Pages: 37-46
Date Published: May 1, 2007


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07-6790-37
Picture of the productA New Route to Electrical Perovskite Lead Titanate from ...
A New Route to Electrical Perovskite Lead Titanate from Lead and Titanium Glycolates via Sol-Gel Process
N. Tangboriboon, A. Jamieson, A. Sirivat, and S. Wongkasemjit

Pure perovskite of lead titanate powder (PbTiO3) was successfully produced via the sol-gel process using lead and titanium glycolates as starting precursors, as directly synthesized by the OOPS process. The obtained lead titanate is tetragonal or the perovskite type, with high purity and with nearly zero moisture content. From the high-resolution mass spectra, the X-ray diffraction technique, and Raman-FTIR coupled with TGA-DTA, the lead-titanium glycolates underwent the sol-gel transition through the formation of Pb-O-Ti bonds. The structural transformation, from the tetragonal form to the cubic form, had a great influence the electrical properties at 430°C, close to the Curie temperature of 490°C. The microstructure of PbTiO3 was characterized by SEM; the particle shape transformed from an agglomerate sphere to a needle and fiber-like shape as the calcination temperature was increased above Tc.

Keywords: Characterization, Sol-Gel Processing, Piezoelectric Material

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0604-25
Picture of the productA New Stress-Induced Martensitic Transformation...
A New Stress-Induced Martensitic Transformation in a Cu-Al-Be Shape Memory Single Crystal
R. Amireche and M. Morin

Stress induced transformation and reversion in a Cu-Al-Be single crystals occurring at room temperature have been studied using the techniques of tensile tests and acoustic emission. Single crystals are 1.8 mm diameter wires with a tensile axis near [100]. Three successive stress induced martensitic transformations have been observed. The reversible cumulated strain due to these three stress induced transformations is higher than 27%.

Complicated stress-strain curves have been explained supposing that the sequence of the three successive stress induced transformations is different between loading and unloading.

Publisher: TMS
Product Format: PDF
Pages: 577-580
Date Published: January 1, 2010


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10-7452-577
Picture of the productA Nitride-Based Reaction for the Formation of a Three-Phase
A Nitride-Based Reaction for the Formation of a Three-Phase Mo-Si-B Alloy
Michael R. Middlemas and Joe K. Cochran

Mo-Si-B intermetallic alloys have the potential of possessing both the oxidation resistance and mechanical properties required for the next generation of jet turbine engine blades. In a novel approach, three-phase alloys of α-Mo, A15 (Mo3Si) and T2 (Mo5SiB2) have been produced through the reaction of molybdenum, Si3N4 and BN powders. Reaction of the starting materials was shown to occur between 1200°C and 1400°C. Densities at 95% of theoretical were achieved by pressureless sintering to 1600°C. This powder metallurgy approach yields a fine dispersion of intermetallics in a molybdenum matrix with grain sizes on the order of 1–4μm, which is not achieved through melt processing routes.

Publisher: TMS
Product Format: PDF
Pages: 63-72
Date Published: May 1, 2007


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07-6660-63
Picture of the productA Novel Process of CNTs-Al2O3 Nanocomposite Ceramics
A Novel Process of CNTs-Al2O3 Nanocomposite Ceramics
Yan Guo, Hoonsung Cho, Yi Song, Jandro Abot, and Donglu Shi

To overcome the disadvantages of processing carbon nanotubes (CNTs) reinforced ceramic composites: 1) CNTs were damaged in high temperature process (>1500°C); 2) Density of CNTs-Al2O3 nanocomposite ceramics was low; 3) Poor CNTs/ceramic matrix bonding. We developed a novel process of CNTs-Al2O3 nanocomposite Ceramics, through plasma surface modification and sintering at ambient pressure. We deposited ultrathin (~2 nm) coatings on Al2O3 nanoparticles and CNTs. Sintering of the plasma treated CNTs-Al2O3 nanocomposite resulted in a density greater than 95% at a low temperature (~1000°C) condition upon optimization of processing parameters. In this way, the mechanical, thermal and electrical properties of carbon nanotubes have be sustained. The underlying sintering/bonding mechanisms at the nano-interfaces have been studied for the consolidated bulk materials. The merit of our research is the engineering of new surface structures of nanoparticles and nanocomposites.

Keywords: CNT, Al2O3 ceramic, Nanocomoposite, Plasma surface modification, Processing

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0604-11
Picture of the productA Novel Thiosulfate System for Leaching Gold Without the Use
A Novel Thiosulfate System for Leaching Gold Without the Use of Copper and Ammonia
J. Ji, C. Fleming, P.G. West-Sells, and R.P. Hackl

The thiosulfate lixiviant system for leaching of gold has been under extensive investigation for nearly two decades and consists of ammonium thiosulfate, copper and ammonia. There are several challenges with this system. The occurrence of ammonia must be taken into account from a health and hygiene aspect in the workplace, and also from an environmental perspective with significant levels of ammonia and copper in the tailings. Copper accelerates the leaching rate but causes excessive thiosulfate degradation. A new lixiviant system that has been investigated consists only of sodium thiosulfate without copper and ammonia. Gold leaching is carried out in an enclosed reactor with slightly elevated oxygen overpressure and temperature. Extensive leaching experiments were carried out to minimize thiosulfate degradation and polythionate formation while maximizing the gold extraction. For the preg-robbing carbonaceous ore sample tested, gold leaching was essentially complete within six hours and the thiosulfate consumption was lower than in the typical ammoniacal thiosulfate system. The gold thiosulfate complex in the pregnant leach solution was found to be quite stable under ambient conditions. This new leaching system has the advantages of being more environmentally friendly, has a shorter residence time, lower thiosulfate consumption, lower oxygen consumption, and is easier to control.

Publisher: TMS
Product Format: PDF
Pages: 227-244
Date Published: August 1, 2003


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03-5549-227
Picture of the productA Parametric Study of Oxy-Fuel Burners in Secondary Aluminum
A Parametric Study of Oxy-Fuel Burners in Secondary Aluminum Melting
M. Huggahalli, N. Saxena, K. Grieshaber, J. Bednarski and D. Stoffel

The use of oxy-fuel burners in secondary aluminum melting applications offers several advantages over air-fuel burners including reduced fuel consumption, faster charge to tap times and lower NOx emissions. Their successful, safe and economical use in a furnace depends on several factors and considerations such as burner and flue placement, metal circulation, charge practices and the type of refractory used in the furnace. These factors required in the successful conversion of furnaces from air-fuel to oxy-fuel based burners are discussed in this paper. Critical parameters are identified and examined using computational fluid dynamics (CFD) simulations. Parameters are estimated via laboratory testing and validated through trials performed at commercial installations. Guidelines and a simplified approach to estimate a priori the economic impact of converting from air-fuel to oxyfuel are presented The final products of this research are simplified and validated tools for modeling aluminum furnaces. These include improved heat and energy balance models and parameterized CFD solutions which provide rapid customization to individual furnace configurations. These tools provide field engineers with immediate and accurate predictions of performance, allowing for repeated precise scenario analyses.

Publisher: TMS
Product Format: PDF
Pages: 185-194
Date Published: February 1, 2002


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01-5131-185
Picture of the productA Passive Film Formed on Alloy 600 as a Steam Generator...
A Passive Film Formed on Alloy 600 as a Steam Generator Tubing Material
Dong-Jin Kim, Hyuk Chul Kwon, Seong Sik Hwang and Hong Pyo Kim

Alloy 600 is used as a material for a steam generator tubing in pressurized water reactors(PWR). In spite of its corrosion resistance under a PWR environment(340°C, 150bar for the primary side and 290°C, 50bar for the secondary side), a stress corrosion cracking(SCC) has occurred on the primary side as well as the secondary side of such a tubing. It is expected that this SCC is related to the electrochemical behavior of the Alloy 600 surface. The present work investigated the electrochemical property of the passive film formed on Alloy 600 as a function of the pH, the dissolved oxygen content, NiB as a SCC inhibitor and PbO as a SCC accelerator by using a potentiodynamic polarization, an electrochemical impedance spectroscopy, a depth profiling by an Auger electron spectroscopy and a transmission electron microscopy. It was found that the oxide thickness and passive state changed with an immersion time of 14 days, based on the kinetics and thermodynamics of the passive film.

Keywords: Alloy 600, steam generator tubing, pressurized water reactor, passivation, SCC

Publisher: Materials Science and Technology Conference (MS&T) 2007
Product Format: PDF
Date Published: September 16, 2007


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08-0703-30
Picture of the productA Physical Model Study for the Two-Phase Flow in a Continuou
A Physical Model Study for the Two-Phase Flow in a Continous Casting Mold
R. Sanchez-Perez, A. Ramos-Banderas, and R.D. Morales

Two-phase flow in a water-air model of a continuous casting slab mold is studied using Particle Image Velocimetry technology. At low gas-loads (mass flow rate of gas/mass flow rate of liquid) fluid flow patterns of phases, gas and liquid, are different and with increases of this parameter both flow fields become similar. In the liquid phase, angles of the jet-root (in front of the SEN's ports) and jet core (main jet-body) are complex functions of the gas flow and casting rates. The first is decreased well below the angle of the SEN's port and the second is increased well above the same angle for all gas-loads. The jet-root angle increases, from small values, while the jet-core angle observes a maximum with the gas flow rate at any casting rate. The jet-core angle approaches to the angle of the SEN's port at high gas flow rates. Accumulation of bubbles is observed in the mold cavity when the casting rate is high at low or high flow rates of gas. Averaged bubble sizes depend on the coalescence-breakup kinetics, which vary with the gas-load. Liquid entrainment by gas to the flux is greatly increased with the casting rate even at low gas-loads. Further understanding of the two-phase flow dynamics should be attained in order to improve the boundary conditions of mathematical models.

Publisher: TMS
Product Format: PDF
Pages: 149-160
Date Published: September 1, 2004


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04-0022-149
Picture of the productA Process for Counteracting the Detrimental Effect of Tetrat
A Process for Counteracting the Detrimental Effect of Tetrathionate on Resin Gold Adsorption from Thiosulfate Leachates
P.G. West-Sells, J. Ji, and R.P. Hackl

Recovery of gold from thiosulfate leachates can be accomplished by adsorption of the gold thiosulfate complex by a strong base resin. Two of the most significant impurities that can decrease this gold adsorption are tetrathionate and trithionate, which are produced as oxidation products of thiosulfate during gold leaching. This paper investigates gold adsorption on a strong base resin (Purolite A500C) as a function of the concentration of these impurities. It is shown that concentrations of tetrathionate and trithionate as low as 150 mg/L can decrease gold loading by an order of magnitude, and that of the two ions, tetrathionate has a stronger detrimental effect. The resin and solution gold concentration profiles were successfully fit using a Freundlich isotherm, which further shows the strong effect of tetrathionate. To counteract the decrease in gold adsorption by tetrathionate, a novel process was proposed. Sulfite was added to the solution to oxidize tetrathionate to trithionate, and a nitrogen blanket was added to ensure that no further oxidation of thiosulfate could take place. It is shown that by incorporating this process, gold adsorption was doubled from both synthetic and real gold thiosulfate leachates.

Publisher: TMS
Product Format: PDF
Pages: 245-258
Date Published: August 1, 2003


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03-5549-245
Picture of the productA Research Study on the Production of Advanced High...
A Research Study on the Production of Advanced High Strength Steels to Heavy Chassis of FH 12 Applied in Auto Structural Parts for the Optimization of Auto Fuel Performance
SH. Pourmostadam

With regard to the achievement of the latest global Technologies for the optimization of energy consumption performance in Autos, Mobarakeh Steel Company , in line with the global studies made on ULSAB (Ultra Light Steel for Auto Body) aiming on the reduction of Max 36% for the ground transportation industry.

Publisher: Materials Science and Technology Conference (MS&T) 2006
Product Format: PDF
Date Published: October 15, 2006


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08-0601-11
Picture of the productA Review of the Chemistry, Electrochemistry, and Kinetics of
A Review of the Chemistry, Electrochemistry and Kinetics of the Gold Thiosulfate Leaching Process
P.L. Breuer and M.I. Jeffrey

Environmental and public concerns and the banned use of cyanide for the recovery of gold in some parts of the world have heightened the search for an alternative lixiviant to cyanide. Thiosulfate appears to be the most promising alternative to cyanide due to thiosulfate being non-toxic, relatively cheap compared to cyanide and generally gold recoveries are similar to those of cyanide. The most widely researched thiosulfate process is one where copper ions and ammonia are added to the solution. This paper reviews the leaching of gold in thiosulfate solutions and the contributions of the research at Monash University to the understanding of the gold oxidation reaction in thiosulfate solutions, the solution chemistry when copper ions, ammonia and oxygen are present, the influence of the changing solution chemistry on the gold leach kinetics, and the application of thiosulfate in the leaching of gold from ores. It is clearly shown that the gold oxidation rate is hindered in thiosulfate solutions. In the presence of copper ions the gold oxidation rate though is significantly enhanced and thus is why copper(II) is more effective than other oxidants in the thiosulfate leach system. The copper-ammoniathiosulfate leach solution chemistry is shown to be very complex, especially in the presence of oxygen as the rate of thiosulfate oxidation increases and the majority of the copper ions are not maintained in the copper(II) oxidation state. The thiosulfate oxidation rate must also be maintained low as an intermediate thiosulfate oxidation product hinders gold leaching. In optimising the recovery of gold from ores with copper-ammonia-thiosulfate leach solutions it is important to evaluate and minimise any negative effect an ore may have on the leach solution chemistry and hence gold leaching.

Publisher: TMS
Product Format: PDF
Pages: 139-154
Date Published: August 1, 2003


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03-5549-139
Picture of the productA Self-Consistent Mean Field Model for Concentration-Depende
A Self-Consistent Mean Field Model for Concentration-Dependent Phenomenological Coefficients: Application to Fe-Ni-Cr Solid Solution
V. Barbe and M. Nastar

KEY WORDS Modeling and simulation, iron and steel, and fundamentals

We present an improvement of the self-consistent mean field (SCMF) approximation of the Lij which extends its applications to alloys presenting high jump frequency ratios. The theory uses an atomic diffusion model which depends on temperature and local composition through thermodynamic and kinetic parameters. We apply it to build a diffusion model of the Fe-Ni-Cr solid solution using high-temperature experimental data. This model is tested on low-temperature resistivity measurements.

This paper is included in TMS Letters,Vol. 2:3 (2005).

Publisher: TMS
Product Format: PDF
Pages: 93-94
Date Published: March 1, 2005


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LET-0503-93
Picture of the productA Software Tool for Teaching Transport Phenomena
A Software Tool for Teaching Transport Phenomena
J.B. Hernández-Morales, R. Fernáandez-Florez, and J.S. Téllez-Martínez

KEY WORDS: Education

Students enrolled in courses on transport phenomena usually solve a large number of problems but do not have the opportunity to explore them in detail, mainly due to time constraints. But solving a closed-form problem does not give the students a feel for the impact of the independent variables on the final result. This deters the development of analytical abilities in the students. Thus, we have developed a user-friendly software tool that allows the student to solve problems in closed form but also permits to change any variable or even to work with a range of values for the relevant variables and plot the results. The software has the capability to handle different units for either input or output in the areas of momentum, heat and mass transfer.

This paper is included in TMS Letters,Vol. 1:5 (2004).

Publisher: TMS
Product Format: PDF
Pages: 89-90
Date Published: May 1, 2004


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LET-0405-89
Picture of the productA Steady State Electrothermic Simulation Analysis of a Carbo
A Steady State Electrothermic Simulation Analysis of a Carbothermic Reduction Reactor for the Production of Aluminium
D.I. Gerogiorgis, B.E. Ydstie and S.S. Seetharaman

Carbothermic production of aluminium is an important alternative to electrolytic processes and has in fact been identified several decades ago as a potentially feasible and profitable process. The cornerstone principle is to take advantage of the endothermic reduction reaction between carbon and alumina instead of resorting to extreme amounts of electric energy to ionize and reduce aluminium oxide to aluminium. Electric energy is necessary only for heating purposes. The present study focuses on constructing and solving a steady-state electrothermic model for obtaining the spatial distributions for electric potential, electric field intensity and temperature. The complex issues of reaction kinetics and multiphase flow are handled by an approximation and are not addressed at the present stage, due to the lack of complete validated models. Because of its inherent complexity, the reaction slag is considered a pseudohomogeneous layer.

An electrothermic simulation encompasses important research challenges, due to the limited knowledge of thermophysical properties for high-temperature multicomponent molten slags.Therefore, thermophysical property modeling and a systematic compilation of published data is a necessary and major first step towards enhancing understanding of the process fundamentals.Models are obtained by analyzing measurement data from numerous literature references for the density, viscosity, thermal and electrical conductivity and specific heat capacity of the slag. The electric potential, field intensity and temperature distributions obtained reveal interesting maxima which indicate localized superheating and lead to important engineering conclusions. The temperature profile calculated will serve as the foundation for the flow problem solution. This computational study will form a basis for future research towards combining the scopes of microscale CFD modeling and mesoscale process modeling into a unified modeling approach.

Publisher: TMS
Product Format: PDF
Pages: 273-282
Date Published: February 1, 2002


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01-5131-273
Picture of the productA Study of a Ni-Mo-Cr-Re Alloy
A Study of a Ni-Mo-Cr-Re Alloy
Pingli Mao, Yan Xin, and Ke Han

This paper describes our recent work on enhancement of mechanical properties of Ni-alloys by optimization of alloys additions, cold work and heat treatment conditions. Hardness test, tensile testing, and microscopy examinations map the influence of alloy additions, cold work and annealing condition on the aging behavior of this Ni-alloy . An additional refractory element to the alloy accelerated the ordering precipitate kinetics significantly in comparison to classic Ni-alloys. The hardness value increases from 200 HV for annealed samples to around 300 HV for samples aged for less than 10 min at 600°C, and then leveled off to 114 hours. Cold work speeds up the nucleation rate of the ordered phase but decreases the precipitates size. When cold deformation increases from 41% to 69%, the average size of Ni2Mo precipitates decreases from 6.5nm to 4.6nm for the major axis and from 3.5nm to 2.6nm for minor axis for samples aged at 600°C for 4 hours.

Publisher: TMS
Product Format: PDF
Pages: 77-85
Date Published: May 1, 2007


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07-6868-77
Picture of the productA Study of Corrosion and Stress Corrosion Cracking of...
A Study of Corrosion and Stress Corrosion Cracking of Carbon Steel Nuclear Waste Storage Tanks
C. Scott, F. Gui, C. S. Brossia, J. Beavers, G. Edgemon, H. Berman, K. Boomer, and G. Frankel

The Hanford reservation Tank Farms in Washington State has 177 underground storage tanks that contain approximately 50 million gallons of liquid legacy radioactive waste from cold war plutonium production. These tanks will continue to be in operation until the waste is vitrified and disposed of at Hanford and the Yucca Mountain Repository.

These nuclear wastes were converted to highly alkaline pH wastes to protect the carbon steel storage tanks from corrosion. However, the carbon steel is still susceptible to localized corrosion and stress corrosion cracking. The waste chemistry varies from tank to tank, and contains various combinations of hydroxide, nitrate, nitrite, chloride, carbonate, aluminate and other species. The effect of each of these species and any synergistic effects on localized corrosion and stress corrosion cracking of carbon steel have been investigated with electrochemical polarization, slow strain rate, and crack growth rate testing. The effect of solution chemistry, pH, temperature and applied potential are all considered and their role in the corrosion behavior will be discussed.

Keywords: Corrosion, Nuclear Waste, Stress Corrosion Cracking

Publisher: Materials Science and Technology Conference (MS&T) 2007
Product Format: PDF
Date Published: September 16, 2007


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08-0703-26
Picture of the productA Study on Electro-Magnetism of Peg-20000 Doped with Nano-Co
A Study on Electro-Magnetism of Peg-20000 Doped with Nano-Cobalt Ferrite Oxide Powder Containing La3+
L. Xiao, Z. Fang, Q.R. Zhang, J.S. Liu, and G.Z. Qiu

Three kinds of nanometer magnetic particles, nano-cobalt ferrite oxide powders and those doped by LaCl3·nH20 with different ratio were prepared by sol-gel method. TGIDTG was applied for investigating thermo-decomposition process of the precursors, which showed that the activation energies of these particles were different in different stage, even not in the same stage for different sample. It has been showed that the magnetic particles with the average diameter less than 100 nm were characterized by XRD and TEM. It indicated that the cobalt ferrite doped with La3+ affected its saturation magnetization and coercive force. The three kinds of nanometer magnetic particles were doped into polymer electrolyte peg-20000 with different rations respectively to obtain the compound substance with optimal conductivity.

Publisher: TMS
Product Format: PDF
Pages: 127-132
Date Published: May 1, 2007


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07-6783-127
Picture of the productA Study on Monotonic and Cyclic Properties of LENS
A Study on Monotonic and Cyclic Properties of LENS Fabricated 4140 and AISI 414 Steel Alloys
G. P. Potirniche, J. Middleton, R. Gomez, B. Bain, H. El Kadiri, H. Rhee, N. Williams, P. Wang, M. F. Horstemeyer

Monotonic and cyclic properties of LENS fabricated 4140 and AISI 4140 steel alloys were analyzed both experimentally and computationally. The LENS 4140 steel was fabricated using a Laser Engineered Net Shaping (LENS) manufacturing technique. Monotonic and cyclic behavior was modeled using an Internal State Variable (ISV) model. The model can simulate plasticity and damage processes at various temperatures and strain rates. The damage evolution is represented by void nucleation, growth and coalescence leading to ductile failure of the material. For low cycle fatigue, damage evolution is governed by the nucleation and growth of voids in front of a crack tip and related with the main crack leading to crack advance.

Publisher: TMS
Product Format: PDF
Pages: 129-138
Date Published: May 1, 2007


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07-6882-129