Novel insights on the grain boundary α phase microstructure formation and orientation development in Ti-6Al-4V alloy

The present work aims to understand the formation of microstructural features and their orientation development at the (prior) β grain boundary regions for Ti-6Al-4V alloy. The grain boundary region in the transformed microstructure primarily contains continuous grain boundary (GB) α phase along with GB α free regions at certain locations. Thin β phase generally separates adjacent GB α variants although it remains absent between many of them. The GB α variants usually follow Burgers orientation relationship (OR) with adjacent β grains although a few of them deviates from following Burgers OR and rather maintain near Potter or Pitsch-Schrader OR with the parent β grains on either side. While the GB α free locations possibly form due to the micro-segregation of β stabilizing elements during liquid→β transformation, the GB α variants without following Burgers OR are likely to associate with strong elemental partitioning during β→α transformation.