Effect of heat treatment on the crystallographic orientation evolution in a near-α titanium alloy Ti60

Abstract

The crystallographic orientation of equiaxed primary α (αp) phase is one of the main factors that determine the final texture/microtexture and mechanical properties for near-α titanium alloys. By annealing a forged Ti60 alloy pancake at 1030 and 1040 °C in the α+β two-phase field, two homogeneous bimodal microstructures were obtained, the intensity of secondary α in the {0001} pole figure increasing with the annealing temperature. In this study, the influence of annealing temperature on the crystallographic orientation evolution in the pancake was studied using an electron backscattered diffraction analysis method. In particular, a misorientation angle θ associated with (βΔJβBOR) that could quantitatively evaluate the deviation of the orientation relationship (OR) between αp and the surrounding β grains from Burgers OR was used to understand the role of the αp phase, which is considered as an anisotropic precipitate, in the texture evolution during annealing in the two-phase field. It was found that the αp grains with small θ are more readily preserved during the annealing, while their pinning effect is relatively small, resulting in faster growth of the neighboring β grains. A possible effect of heterogeneous local orientation distribution on the microstructure during the annealing process is also discussed.