Slip initiation in interlayered β and corresponding slip transfer during compression of a lamellar-structure titanium alloy

Abstract

The scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were used for a quasi in-situ observation on the slip trace and crystallographic orientation at four strains during the compression of a widmannstätten-structure α/β titanium alloy. The previous investigations suggested that the slip always initiated in lamellar α prior to interlayered β due to the lower yield strength and higher Young's modulus of HCP α phase. Interestingly, it is found that the slip initiates in the interlayered β prior to lamellar α within the α colony in this work. Meanwhile, the preferential slip initiation in interlayered β does not occur at the highest Schmid factor (SF) which is calculated by the applied stress. The preferential slip in interlayered β is related to the heterogeneous deformation among different α colonies, which is related to the distribution of deflection angle θ between loading direction and c-axis of α phase. The slip transfers from interlayered β to lamellar α indirectly, which not only requires a good collaboration between SF and geometric compatability parameter (m'), but also needs a large accumulation of deformation in interlayered β.