Effect of grain size on α-variant selection in a ZrTiAlV alloy

Local crystallographic orientation characteristics of grains with different sizes in a ZrTiAlV alloy after interrupted cooling from β phase region are investigated by electron backscatter diffraction (EBSD) technique. A statistical analysis of EBSD data shows that bigger parent β grains present weaker variant selection than smaller grains. The relevant influences are studied by comparing the nucleation behavior of grain boundary α (GBα) and succedent growth stage in varisized grains. In-depth analysis indicates that the deviation between pole of GBα and common pole of adjacent parent β grains is responsible for the smaller degree of variant selection inside the bigger parent β grains. The formation of more than one GBα type at the β/β grain boundary with common pole in bigger grains results in obstructing each other for these variants during the following growth stage, while only one type of GBα nucleate at the β/β grain boundary with common pole in smaller grains and it can freely grow into the interior of the grains, leading to stronger variant selection in smaller β grains.