Analysis of strain localization and slip transfer based on composite Schmid factor in TA19 titanium alloy

Abstract

The correlation between slip behavior and strain localization was investigated through in-situ tensile experiment. The relationship between slip transfer and crystallographic orientation was analyzed using the composite Schmid factor (CSF), where CSF=mout+minm' (min and mout represent the Schmid factor (SF) of incoming and outgoing slip systems, respectively, m' is the geometric compatibility factor). The results show that for adjacent equiaxed α (αeq) grains without slip transfer, it will induce significant strain localization around αeq/αeq grain boundary due to the accumulation of massive dislocations on grain boundary. The initiation of secondary slip in αeq grain would exacerbate strain localization within the grain, as it promotes the dislocation pile-ups and entanglement. The slip behavior is largely related to the crystallographic orientation of the two adjacent αeq grains. Based on statistical analyses, for slip transfer, the slip system with the largest CSF is more likely to act as an easily initiated outgoing slip system. It can be attributed to that the CSF could reflect the synergistic effect of applied stress and the local shear stress induced by incoming slip system on the slip transfer behavior. However, with the increase of strain, some outgoing slip systems without the largest CSF can also be initiated, which may be associated with the complicated local stress state induced by the initiation of slip systems in multiple adjacent αeq grains before the initiation of outgoing slip system.