Surface Morphology associated with Phase Transformations in Indium-Rich Solid Solutions

Abstract

The structural changes and surface morphology concerning phase transformations in indium-rich solid solutions, such as In–Tl, In–Cd, In–Pb, In–Sn and In–Hg, have been studied by means of crystallographic and metallographic methods. Four types of phase transformation are observed in indium-rich solid solutions as follows: (1) fcc\ ightleftarrowsfct (c⁄a>1), (2) fcc\ ightleftarrowsfct (c⁄a<1), (3) fct (c⁄a<1)\ ightleftarrowsfco\ ightleftarrowsfct (c⁄a>1) and (4) fct (c⁄a<1)\ ightleftarrowsfct (c⁄a>1). All the transformations, except the fco\ ightleftarrowsfct (c⁄a>1) one, are of martensitic type, and the alloy surface of low-temperature phase shows a surface relief associated with the phase transformation, which is ascribed to a banded structure due to {110} transformation twinning. Under an assumption that these transformations take place in the form of a kind of the Bain lattice deformation, the lattice correspondence and the orientation relation between high- and low-temperature phases are well explained with respect to each phase transformation. The crystallographic orientation of the twin plane is explained on the basis of the Sapriel theory available for ferroelastic substances.