In-situ investigation on tensile deformation and fracture behaviors of Ti60 alloy rolled sheet with equiaxed microstructure

In this work, the deformation mechanism and fracture behavior of Ti60 alloy sheet with equiaxed micro-structure (the volume fraction of equiaxed alpha grains is 68%) using the in-situ tensile test were studied by in -situ scanning electron microscope (SEM) and electron backscattering diffraction (EBSD). The results show that equiaxed alpha grains activate three coordinated deformation mechanisms, mainly single slip mode, supplemented by slip transfer and grain rotation. The alloy is mainly coordinated by equiaxed alpha grain de-formation, dominated by prismatic < a > and basal < a > slip, and prismatic slip in (1010) plane and [1210] direction as the most active slip system. With the increase of deformation, the soft oriented equiaxed alpha grains preferentially occur prismatic slip, while some hard oriented grains rotate in the direction favorable to slip. When there is no slip transfer between adjacent grains, dislocation pile-up at the grain boundary and causes stress concentration, which makes the grain boundary easy to become the crack nucleation point. In SEM and EBSD studies, lamellar alpha grains have no obvious deformation characteristics. However, TEM study found that some lamellar alpha grains were kinked, which led to lamellar fracture and the formation of high-density dislocation areas around them. Meanwhile, due to the large difference in coordinated deformation ability between equiaxed alpha grains and lamellar alpha grains and between equiaxed alpha hard and soft oriented grains. Therefore, cracks are initiated, propagated and fractured mainly at the junction of the alpha colony composed of lamellar alpha grains and at the equiaxed alpha grain boundary.(c) 2022 Elsevier B.V. All rights reserved.