Phenomenological considerations of phase transformations in indium-rich alloys

Indium-rich alloys containing solute atoms such as Cd, Hg, Tl, Sn and Pb undergo four kinds of phase transformation: (1) fcc→fct (c/a>1), (2) fcc→fct (c/a<1), (3) fct (c/a<1)→fco→fct (c/a<1) and (4) fct (c/a<1)→fct (c/a>1). We have investigated these phase transformations using a phenomenological theory based on the Landau-theory of phase transformation. The appearance of all the phase in indium-rich alloys is well explained phenomenologically, and all the phase transformations are shown to be expressed by two thermodynamic parameters in the phase diagram. Some physical quantities such as the spontaneous strain, the elastic constant C’ and the change in entropy are calculated and are compared with the experimental results. The dependence of the transformation temperature on the stress and the stress strain relation are also obtained.