Growth behavior and variant selection of grain boundary α in Ti6246

Abstract

The grain boundary α (αGB) in titanium alloys is believed to significantly impact the subsequent β → α transformation, the evolution of α microtexture and the final mechanical properties. The αGB with remained β phase has been generally observed in Ti-6Al-2Sn-4Zr-6Mo and other α + β titanium alloys. In this study, the growth behavior and variant selection of αGB formed by β processing were investigated by the interrupted furnace cooling experiment. In the early growth period of the αGB, discontinuous chevrons αGB particles grew, which was significantly associated with Mo element distribution. Besides, the double-Burgers orientation relationship (2-BOR) variant selection criterion according to the θ2-BOR (misorientation of the close-oriented αGB variant pair of parent β1 and β2) deviation is refined in this study. At β grain boundary with θ2-BOR deviation below 8º, the αGB orientation is 100% predicted. In this case, the αGB grains are always close to the closest theoretical variant pair of both sides β grains. When θ2-BOR is over 14º, the criterion is not predictive.