Antiphase domain growth in Cu 3Au: Quantitative comparison between theory and experiment

Abstract

The Hillert theory of normal grain growth has been modified for antiphase domain (APD) growth in Cu 3Au. A semi-empirical correction factor, β, is introduced into the theory in order to incorporate the effect of the extreme breadth of the experimentally observed APD size distributions on the rate of APD growth. The mobility. M, of APD boundaries in an ordered alloy, which is proportional to the chemical diffusion coefficient, \\ ̄ tD, is shown to be inversely proportional to the long-range order parameter, S. The theory is compared with literature data on APD growth in Cu 3Au, as well as our own measurements made at 325, 350 and 375°C for times up to 10 h on pure Cu 3Au and Cu 3Au-Co alloys containing 1.5 and 2.5 at.%Co. Using estimated values of \\ ̄ tD, measured values of S, values of β determined by fitting the theory to existing APD distributions and another parameter 〈 u〉 which is a measure of the relative values of the average and ‘critical’ APD sizes, the experimentally measured rate constants for APD growth were used to calculate values of the APD boundary interfacial energy, σ, for comparison with recently derived theoretical values. The quantitative agreement between theory and experiment is satisfactory, considering the uncertainty in \\ ̄ tD. The theory also predicts that APD growth should increase in the Co-containing alloys. Such an effect is observed experimentally, but is greater in magnitude than predicted by the theory, for reasons that are not understood.