Study of ideal strengths of metals and alloys by statistical moment method: Temperature dependence

2007 ◽  
Vol 22 (8) ◽  
pp. 2230-2240 ◽  
Author(s):  
Vu Van Hung ◽  
K. Masuda-Jindo ◽  
Nguyen Thi Hoa
Keyword(s):  
Temperature Dependence ◽  
Moment Method ◽  
Density Functional ◽  
Tight Binding ◽  
Statistical Moment ◽  
Metals And Alloys ◽  
The Body ◽  
Energy Relation ◽  
Transition Elements ◽  
Statistical Moment Method

The ideal strengths of metals and alloys at finite temperatures have been studied using the statistical moment method. The tensile and shear strengths of the body-centered cubic (bcc) transition metals like Mo and W (refractory metals), and ordered FeAl (B2) and Fe3Al (DO3) alloys are calculated as a function of the temperature. The orthogonal tight-binding method is used for bcc transition elements, while the universal binding-energy relation (UBER)-type of pairwise potentials, derived from ab initio density-functional theory, is used for the FeAl and Fe3Al alloys. We discuss the temperature dependence of the tensile and shear strengths of the metals and alloys in conjunction with those of the second-order elastic constants.

Application of Statistical Moment Method to Thermodynamic Properties and Phase Transformations of Metals and Alloys

2008 ◽  
Vol 138 ◽  
pp. 209-240 ◽  
Author(s):  
K. Masuda-Jindo ◽  
Vu Van Hung ◽  
P.E.A. Turchi
Keyword(s):  
Thermodynamic Properties ◽  
Phase Transformations ◽  
Moment Method ◽  
Structural Phase ◽  
Equilibrium Phase ◽  
Statistical Moment ◽  
Metals And Alloys ◽  
Thermodynamic Quantities ◽  
Specific Heats ◽  
Statistical Moment Method

The thermodynamic properties and phase transformations of metals and alloys are studied using the statistical moment method, going beyond the quasi-harmonic approximations. Including the power moments of the atomic displacements up to the fourth order, the Helmholtz free energies and the related thermodynamic quantities are derived explicitly in closed analytic forms. The thermodynamic quantities, like thermal lattice expansion coefficients, specific heats, Grüneisen constants, elastic constants calculated by using the SMM are compared with those of other theoretical schemes and the experimental results. The hcp-bcc structural phase transformations observed for IVB elements, Ti, Zr and Hf, are discussed in terms of the anharmonicity of thermal lattice vibrations. The equilibrium phase diagrams are calculated for the refractory Ta-W and Mo-Ta bcc alloys. In addition, the temperature dependence of the elastic moduli C11, C12 and C14 and those of the ideal tensile and shear strengths of the bcc elements Mo, Ta and W are studied: We also discuss the melting transitions of metals and alloys within the framework of the SMM and estimate the melting temperatures through the limiting temperature of the crystalline stability.

THE DIFFUSION IN FCC BINARY INTERSTITIAL ALLOY

2020 ◽  
Vol 65 (10) ◽  
pp. 18-23
Author(s):  
Hoc Nguyen Quang ◽  
Loan Pham Thi Thanh ◽  
Viet Nguyen Tuan ◽  
Le Nguyen Ngoc
Keyword(s):  
Diffusion Coefficient ◽  
Moment Method ◽  
Interstitial Atom ◽  
Diffusion Theory ◽  
Correlation Factor ◽  
Statistical Moment ◽  
Analytic Expressions ◽  
Fcc Metal ◽  
Statistical Moment Method

We build the theory of diffusion for FCC binary interstitial alloy under pressure based on the statistical moment method, where there are the analytic expressions of the jumping frequency of interstitial atom, the effective jumping length, the correlation factor, the diffusion coefficient, and the activated energy. In limit cases, we can obtain the diffusion theory for FCC metal A under pressure.

scholarly journals Critical Temperature for Ordered-Disordered Phase Transformation in Cu3Au under Pressure

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Pham Dinh Tam ◽  
Bui Duc Tinh ◽  
Nguyen Quang Hoc ◽  
Pham Duy Tan
Keyword(s):  
Experimental Data ◽  
Phase Transformation ◽  
Critical Temperature ◽  
Moment Method ◽  
Statistical Moment ◽  
Disordered Phase ◽  
Good Agreement ◽  
Statistical Moment Method

We use the statistical moment method to study the dependence of the critical temperature Tc for Cu3Au on pressure in the interval from 0 to 30 kbar. The calculated mean speed of changing critical temperature to pressure is 1.8 K/kbar. This result is in a good agreement with the experimental data.

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