Microstructure evolution and tensile properties of as-rolled TiB/TA15 composites with network microstructure

Abstract

To investigate the microstructure evolution and mechanical properties of DRTMCs with network microstructure during the rolling deformation, the TiB whiskers reinforced Ti-6.5Al–2Zr–1Mo–1V (TA15) composites (TiBw/TA15) with the addition of silicon element and different TiB volume fractions were successfully fabricated by hot pressing sintering and rolled in the α+β region. Compared with the as-sintered composites, the as-rolled composites presented the lower local TiBw content, higher matrix connectivity, remarkable grain refining and larger silicides. After rolling deformation, the room-temperature ultimate strength and fracture elongation were dramatically improved. The as-rolled 3.5 vol.% TiBw/TA15 composite obtained better combination properties of 1248 MPa and 10.5% at room temperature. The increase in strength can be attributed to grain refining of the matrix, directional distribution of TiBw, and stronger hinder of silicides. The enhancement of ductility was due to increasing matrix connectivity, grain refining as well as DRX behavior of bimodal microstructure. As for high-temperature properties, the tensile strengths increased by 26–32% at 600 °C and 20–32% at 650 °C after rolling, which is also attributed to directional distribution of TiBw, grain refining of matrix and larger silicides. The highest strengths at 600 °C and 650 °C are 820 MPa and 698 MPa, respectively. The fracture behavior of the composites was discussed in detail. • As-sintered and as-rolled TiBw/TA15 composites with excellent metallurgical bonding were achieved. • Room temperature strength and ductility of the composites were simultaneously improved a lot after rolling. • Flat network microstructure continued to exert the reinforcement and strain bearing of bi-connected structure after rolling. • TiB rotation, larger silicides and refined grains during rolling deformation contribute to the strength enhancement.