Effects of solution treatment on microstructure and properties of Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta titanium alloy

Abstract

This study investigated the effects of solution treatments under various conditions on the matrix and silicides microstructure and their impact on the mechanical properties of high-temperature Ti60 (Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta) titanium alloy. The microstructure evolution during solution treatments was characterized, and the tensile properties at 600 °C and room temperature (RT) were investigated. The results show that the fraction and grain size of martensite and silicides can be tailored through solution treatments. With increasing solution temperature, the fraction of primary α (α_p) phase and silicides decreases, while that of the transformed β (β_t) microstructure increases. After solution treatment at 1025 °C, the yield strength (YS) and ultimate tensile strength (UTS) reach 685.0 MPa and 900.8 MPa, respectively, at 600 °C, increasing by 18.0 % and 27.0 %, respectively, compared to the initial state. The elongation (EL) remains at 16.2 %. The strengthening mechanisms of Ti60 alloy include grain boundary strengthening of the α_p phase and martensite formed during rapid cooling, as well as precipitation strengthening of the silicides. With increasing solution temperature from 950 °C to 1025 °C, the fraction of martensite strengthening increases from 38.4 % to 89.3 %, while the fraction of precipitation strengthening of silicides decreases from 3.63 % to 1.17 %.