Precipitation behaviors and orientation evolution mechanisms of alpha phases in Ti-55511 titanium alloy during heat treatment and subsequent hot deformation

摘要

The precipitation orientation of alpha phases in a Ti-55511 alloy during the heat treatment and the subsequent hot deformation is investigated. It is observed that the beta grains prominently influence the precipitation process of alpha phases, i.e., for the neighbouring beta grains without similar {110} pole, the precipitation orientation of grain boundary (GB) alpha phases (alpha(GB)) keep {0001}/{110}beta 1 or {0001}/{110}beta 2 to maintain the burgers orientation relationship (BOR) with the neighbouring beta grains. For the neighbouring beta grains with similar {110} pole, the {0001} poles of alpha(GB) phases precipitate parallel to this similar {110} pole and maintain BOR with the neighbouring beta grains. For the neighbouring beta grains with multiple similar {110} poles, the {0001} poles of alpha(GB) phases precipitate along these similar poles and maintain BOR with the neighbouring beta grains. Besides, the interface instability nucleation and sympathetic nucleation are the main nucleation modes of the GB widmanstatten alpha phase (alpha(wGB)), which primarily precipitate within beta grains with the similar orientation of alpha(GB) phases. The intracrystalline widmanstatten phase (alpha(wI)) precipitate in a single beta grain with 12 precipitation orientations. The BOR between alpha(wI) phases and beta grains is destroyed during the subsequent hot compressive deformation.