Static grain growth in a microduplex Ti-6Al-4V alloy

The grain growth behavior of the microduplex titanium, 6% aluminum, 4% vana dium alloy is addressed. Although there has been considerable work done on second phase particle coarsening, there is Limited research on coarsening i n a two-phase material with nearly equal phase ratios. In this study, coars ening parameters were determined for the temperature range of 850-925 degre es C, where alpha and beta phase ratios are approximately 50 percent. Exper imentally determined grain growth data for the Ti alloy are found to follow classical particle-stabilized grain growth kinetics with a temperature dep endent coefficient and a constant exponent. On the basis of these observati ons a grain boundary pipe diffusion model is proposed which has the desired features of incorporating both the faster kinetics of the grain boundary d iffusion and the unidirectional exponent q = 5, which is often observed in microduplex alloys. The model appears to resolve a previously reported dile mma that the time exponent suggests pipe diffusion bur the kinetics associa ted with the triple boundary is too slow. The concept proposed should have applicability to other two-phase alloys containing approximately equal volu me fractions of each phase. (C) 1998 Acta Metallurgica Inc. Published by El sevier Science Ltd. All rights reserved.