Эволюция кристаллографической текстуры в титановом сплаве ВТ6, подвергнутом плоской прокатке

Abstract

This work presents the results of experimental studies and computer modeling of the crystallographic texture evolution in the billets of titanium alloy VT6, subjected to plane rolling in the coarse-grained and ultrafine-grained (UFG) states. UFG state has been formed by the method of multiaxial isothermal forging at 650°С with the number of cycles equal to 6. Plane rolling was performed until the reduction equal to 75% and 95% at 550°С. The analysis of pole figures revealed that plane rolling of UFG state, unlike in the coarse-grained state, promotes the orientation of grains with basal plane substantially parallel to the rolling plane. Modeling of pole figures within the viscoplastic self-consistent model, implemented in the Voce framework, allowed to determine the active slip and/or twinning systems depending on the reduction at plane rolling. It is shown that prismatic slip system, tensile and compression twinning systems are the most active systems at plane rolling of the investigated alloy in the coarse-grained state. At the same time, the dislocation activity of the basal and pyramidal <a> slip systems is observed at high degrees of reduction at plane rolling. In the case of UFG state, prismatic, pyramidal <a+c> of the first order and the basal slip systems are active. The processes of tensile and compression twinning are also implemented in initial stages of plane rolling, but their activity is rather low at high degrees of deformation.