Kinetics of the low-temperature structural transformation in the In–4.3 at. % Cd solid solution

Abstract

The reversible structural transformation of the hysteretic type observed previously by the authors in the In–4.3 at. %Cd alloy on low-temperature thermocycling is investigated further. In the hysteresis region (150–290 K) a pronounced instability of the macroscopic characteristics of the alloy is observed, which is manifested as time dependence of the dynamic Young’s modulus and resistivity of the samples at a constant temperature fixed during the cooling or heating run. The kinetic effects are investigated in detail near the boundaries of the hysteresis, where they are most clearly expressed. Less clear signs of the structural transformation are observed on the temperature dependence of the microhardness of the alloy. It is found that the structural transformation is governed by thermally activated processes with several characteristic relaxation times: the analytical form of the kinetic curves and the temperature dependence of the relaxation times are substantially different for the direct (on cooling) and reverse (on heating) transformations. Similarities and differences between this transformation and the known structural rearrangement processes in the physics of alloys are discussed. The structural transformation investigated here is also discussed in relation to the phase diagram of the In–Cd system.