Effects of Composite Processing at Room Temperature and Heat Treatment on Microstructure and Mechanical Properties of Ti-53Nb Alloy

The bars of Ti-53Nb alloy were prepared by combined deformation method of room temperature equal channel bending channel deformation (ECAP)+cold rolling+cold rotary swaging. The evolution of microstructure and β-crystal growth were studied by metallographic microscope (MM), scanning electron microscope (SEM) and uniaxial tensile test after preparing process. The effects of work hardening and fine grain strengthening were analyzed with dislocation strengthening theory and Hall-Petch theory. The results show that the tensile strength increases from 380 MPa to 553 MPa before and after deformation and heat treatment, increased by 45.53%, and the elongation reaches 16%. The growing speed of β-crystal is accelerated with increasing the solid solution temperature, and the grain size dependence of strengthening follows the Hall-Petch equation. The microstructure exhibits uniform equiaxed grains after annealing at 700℃ for 60 min, which can match the requirement of strong plastic characteristics in applications.