Evolution of microstructure and high temperature tensile properties of as-extruded TiBw reinforced near-α titanium matrix composite subjected to heat treatments

The TiBw reinforced near-α titanium matrix composite (Ti-5.8Al-3.4Zr-4.0Sn-0.4Mo-0.4Nb-0.4Si-0.06C) was successfully synthesized by powder metallurgy and hot extrusion route. The effects of solution and aging temperature on the microstructure and high temperature tensile properties of the composite were investigated. The results revealed that the fine transformed β phase can be obtained by the solution treatment at β phase region and aging treatment, no other precipitates were observed. The α2 phase (Ti3Al) can be acquired when the solution treated at α+β phase region followed by aging treatment. With increasing the aging temperature from 500 to 700°C for 5 h, the size of α2 precipitates increases from about 5 to about 30 nm. The TiBw are stable without any interfacial reaction during the heat treatments. The high temperature tensile properties show that the composite performed by solution and aging treatment exhibits good strengthening effects. With increasing the aging temperature from 500 to 700°C, the strength of the composite increases at the expense of elongation due to the increment of α2 precipitates. The strength of the composite at 600°C increases by 17% to 986 MPa after 1000°C/2 h/AC and 700°C/5 h/AC heat treatment.