Thermodynamics and X-ray studies of indium-thallium alloys

Abstract

In the present investigations x-ray and thermodynamic studies have been conducted for the In-T1 alloys in the composition range of 16.0 to 22.0 atom percent T1. The thermodynamic studies result in direct determination of all thermodynamic parameters including the enthalpy and free energy of fcc to fct transformations for the above alloy compositions. From the results of x-ray investigation the lattice parameters of the low temperature phase (which is fct) have been determined for all alloy compositions. The enthalpy of phase transformation and the transformation temperatures bears a straight line relationship with the volume change. This seems to indicate that the strain free energy increases in the alloys containing larger percentage of T1. This increase in strain free energy increases the non-chemical free energy change associated with the transformation. For the transformation to take place the chemical free energy change must overcome the non-chemical free energy change. This is obtained by increasing the degree of undercooling. The free energy of mixing Δ Fm* curves show significant variation which have been interpreted in terms of short range order parameter.