Kink band formation mechanism in α/β Ti-9Cr two-phase alloy

Abstract

A combination of experimental and numerical studies was carried out to understand the microstructure and formation mechanism of kink bands in α/β two-phase titanium alloys. A deformation kink band was introduced in a Ti-9Cr alloy after uniaxial compression test. The strength changes of the α and β phases inside and outside the kink band were evaluated by nanoindentation tests. A potential hardening effect was revealed in the α phase inside the kink band, while a possible softening effect was located in the β phase at the kink boundaries. Microstructural examination of the kink band was conducted by electron backscatter diffraction measurement. The crystal rotation axis was found to be perpendicular to both the (0001) basal plane of the α phase and one of the (110) planes of the β phase. The crystallographic features were characterized by transmission electron microscopy observation, revealing a prismatic 〈a〉 slip that occurred during the compression to accommodate the rotations around the c-axis. Nanoindentation tests were performed on an undeformed specimen to calibrate the crystal plasticity model. A crystal plasticity finite element model was developed and {110}β-rotation-type kink bands were reproduced in the simulation and confirmed the prismatic slip activity.