Hot and cold rolling of a novel near-α titanium alloy: Mechanical properties and underlying deformation mechanism

Abstract

In this work, mechanical properties, microstructure evolution mechanism, texture variation process and deformation mechanism of a near-α CT20 titanium alloy with different hot and cold rolling reductions are investigated and uncovered comprehensively. The tensile strength of the alloy gradually increases, and the ductility decreases as the rolling reduction grows along both rolling direction (RD) and transverse direction (TD) due to the increase in grain boundary and dislocation density, while the mechanical properties along RD are better than those along TD. The high strain carried in α phases reduces the proportion of high-angle grain boundaries and increases the content of low-angle grain boundaries, with growing dislocation density in α phase. During cold rolling process, basal <a> slip shifts {0001} pole toward ND, and prismatic <a> slip inclines {11 2‾0} pole and {10 1‾ 0} pole toward TD. The intragranular orientation is enhanced with increasing rolling reduction, and the texture intensity of α and β phase is weakened as rolling reduction gradually grows. It is also noteworthy that prismatic <a> slip dominates the slip mode along RD, while basal <a> slip and pyramidal slip are activated along TD during cold rolling. The work-hardening rates of cold-rolled alloys are higher than that of the hot-rolled alloy as a large number of dislocations and grain boundaries were introduced by severe plastic deformation. The different work-hardening rates and mechanical properties of the rolled alloy along RD and TD are verified to be associated with the preferred orientation of α phase and the slip distances of dislocation during deformation.