Powder metallurgy fabrication and heat treatment modification of (TiBw+(TiZr)<sub>5</sub>Si<sub>3</sub>)/TA15 composites

Abstract

Network structured (TiBw+(TiZr)5Si3)/TA15 composites were successfully fabricated using powder metallurgy. This addresses the need in the aerospace and national defense fields for structural materials that are light-weight, heat-resistant, high-strength, and tough. The results showed that in-situ synthesized TiB whisker (TiBw) reinforcement was distributed around TA15 titanium alloy particles, forming a microstructure network. The titanium-zirconium-silicide (TiZr)5Si3 reinforcement was mainly distributed near the α/β phase interface. By improving the grain and phase boundary strengthening effects, solving the high-temperature weakening effects of the grain and phase boundary, and effectively inhibiting the growth of titanium alloy grains and α phase particles, the strength and ductility of the (TiBw+(TiZr)5Si3)/TA15 composites were significantly improved when compared the as-sintered TA15 titanium alloy (at room temperature and high temperatures). The tensile strength at 600oC was increased by 50% and the fracture strain by 58% when compared to TA15 titanium alloy. Furthermore, the high-temperature strength and ductility of the composites can be substantially improved by solid solution and aging heat treatments. This can modify the morphologies of TA15 matrix and (TiZr)5Si3 reinforcement. After a solid solution and aging heat treatment of 1100oC / 40 min /WQ+ 600oC / 5 h /AC), a tensile strength of 1010 MPa at 600oC, and a fracture strain of 38.5% at 700oC were achieved for the network structured (TiBw+(TiZr)5Si3)/TA15 composites. The strength enhancement after heat treatment is mainly attributed to the formation of the transformation β microstructure, solution strengthening, and dispersion strengthening caused by aging precipitation in the second phase. The improvement of high-temperature ductility is mainly due to the microstructure refinement and the coordinated deformation improvement.