The Order-Disorder Transformation in Cu3Au at High Pressure

The order-disorder transformation in the alloy Cu3Au has been studied at pressures ranging up to 21 kbar by means of electrical-resistance measurements made while the sample is at high temperature and under pressure. The rate of change of the critical temperature with pressure is 2.1°K/kbar from 7 to 21 kbar. The kinetics of the order transformation below Tc are adequately described by the homogeneous reaction rate equation and an activation volume of 6.8 cm3/mole of atoms. The magnitude of this activation volume indicates that the formation of vacancies on the gold sublattice is the rate-limiting step in the homogeneous ordering process.