Effects of heat treatments on microstructure and tensile properties of as-extruded TiBw/near-α Ti composites

The effects of different heat treatments on the microstructure and tensile properties of the as-extruded TiBw/Ti60 composites have been investigated. Without solution treatment, the alpha(2) phase precipitated from alpha phase and mounts of elliptical S-2 suicide are formed at the interface of alpha/beta phases after aging at 700 degrees C for 5 h, which results in clear enhancement of strength at 700-800 degrees C. After the solution and aging treatment, more alpha(2) phase precipitates from ao phase and less spherical S-2 suicide precipitated from the body of both alpha(p) and transformed beta phase. Moreover, some small silicide precipitates are formed from a matrix near the TiBw due to the stacking faults and the interface effect. The TiBw are stable without any interfacial reaction during the heat treatments. The results show that the composites performed by solution and aging treatment exhibit high strength (1377 MPa) and low elongation (2%). The annealing treatment can soften the composites and increase the elongation to 7%. (C) 2015 Elsevier Ltd. All rights reserved.