Romesh C. Sharma

Thermodynamic analysis and phase equilibria calculations for the Zn-Te, Zn-Se and Zn-S systems

Abstract The available thermodynamic and phase equilibria data for the binary systems Zn-Te, Zn-Se and Zn-S have been analyzed using an “associated solution model” for the liquid phases and considering the ZnTe, ZnSe and ZnS phases as line compounds. The phase diagrams and thermodynamic properties calculated from the optimized phase parameters agree well with the experimental data.

The effect of alloying elements on pearlite growth

The model developed by Sharma 1 and Sharmaet al. 2 for the mechanism of pearlite growth in ternary Fe-C-Cr alloys has been extended to other systems. Detailed thermodynamic and semi-empirical kinetic calculations have been carried out to determine pearlite growth rates for a number of Fe-C-X alloys (X = Mn, Cr, Ni, Si) and compared with the experimental data from the literature. It has been shown that the pearlite growth is, in general, controlled by the alloying element boundary diffusion at low supersaturations and carbon volume diffusion at high supersaturations, as predicted by the model. The transition temperature between the two mechanisms is a function of the amount and type of alloying element.

Phase equilibria calculations of AlSb, AlGa and AlGaSb systems

Abstract A quasi sub-subregular solution model is used to describe thermodynamic properties of the liquid phases in Al-Sb, Al-Ga and Al-Ga-Sb systems. An essentially stoichiometeric compound, AlSb, in the Al-Sb binary system is considered as a line compound and the ternary compound, (AlyGa1−y)Sb, in Al-Ga-Sb system is described as a regular solution of stoichiometeric compounds, AlSb and GaSb. The model parameters for different phases are obtained by simultaneous optimization with respect to the available thermodynarnic and phase equilibria data of these systems. Phase diagrams and thermodynamic data are, then, calculated by using the optimised model parameters and compared with the experimental data.

Thermodynamic Analysis and Phase Equilibria Calculations for the Cd‐Te, Cd‐Se, and Cd‐S Systems

The authors present an analysis of the available thermodynamic and phase equilibria data for the binary systems Cd-Te, Cd-Se, and Cd-S using an associated solution model for the liquid phases and considering the CdTe, CdSe, and CdS phases as line compounds. The phase diagrams and the thermodynamic properties calculated from the model parameters agree well with the experimental data.

Phase equilibria calculations of AlIn and AlInSb systems

Abstract Thermodynamic properties of the liquid phases in Al-In and Al-In-Sb systems have been assessed by using quasi sub-subregular solution model and (AlyIn1−y) Sb phase in the Al-In-Sb system is considered as a regular solid solution of AlSb and InSb compounds. Thermodynamic properties and phase diagrams of these systems calculated by using the optimised model parameters agree well with the available experimental data.

Phase equilibria calculation of Zn-Cd-Te system

Abstract A quasi subregular associated solution model is used to describe thermodynamic properties of the liauid phase in Zn-Cd-Te system. The ternary compound. (Zn y Cd 1−y )Te, is described as a subregular solution of stoichiometric compounds. ZnTe and CdTe. The model parameters for different phases are obtained by simultaneous optimization with respect to the available thermodynamic and phase equilibria data. Phase diagrams are. then, calculated by using the optimized model parameters and compared with the experimental data.

analytical expressions for the activity of the solute in binary dilute solutions in terms of associated solution model parameters

Simple analytical expressions have been derived to express the activity of the solute in binary dilute solutions in terms of the Associated Solution Model (ASM) parameters. The activity coefficient of the solute at infinite dilution and the first and second order Wagner’s self-interaction parameters are, then, given as a function of ASM parameters for some simple cases.

Age Hardening Behavior in Al-8Zn-2Mg-2Cu Wrought Aluminum Alloy

Aluminum alloys based on Al-Zn-Mg-Cu system classified under high strength light alloys, find a large scale application in aerospace sector. In the present study, heat treatment of an Aluminum alloy with Al-8Zn-2Mg-2Cu wt.% (AA7449) was carried out. Heat treatment parameters were optimized based on hardness and conductivity measurements. The mechanisms of strengthening in primary and secondary aged states are explained using hardness and conductivity measurements. Conductivity generally showed an increasing trend with increase in aging time, which could be attributed to decrease in the lattice distortion of the Aluminum matrix with increase in aging time. The dissolution of GP zones and formation of other metastable phases like η’ and stable phase like η were found to reduce the supersaturation in the matrix as the precipitation growth and coarsening processes are completed during overaging. Transmission electron microscopy (TEM) study was carried out to confirm the peak-aging regime. Selected Area Diffraction (SAD) patterns were recorded where GP zones and η’ precipitates were observed in the bright field images to establish their nature. The mechanical properties were correlated with the TEM observations and was suggested that a critical distribution of GP zones and η’ precipitates is essential to achieve peak strength in Al-Zn-Mg alloys.