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

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