Significantly strengthening the Ti₇₀Nb₁₀Mo₁₀Zr₁₀ alloy via architecting two-scale silicide reinforcements

To further strengthen the Ti₇₀Nb₁₀Mo₁₀Zr₁₀ alloy (denoted as TI70 alloy) with a single BCC solid solution microstructure, two-scale silicide reinforcements were successfully tailored by adding 1 at.%, 2 at.% and 4 at.% Si element during powder metallurgy process (denoted as TI70-Si_x alloys). The nano-scale S1-type (Ti,Zr)₅Si₃ silicides were precipitated and distributed dispersively at grain interior to provide dispersion strengthening effect, while the nano-scale and micro-scale S2-type (Ti,Zr)₆Si₃ silicides were distributed at the grain boundaries and formed a novel network microstructure which could prohibit grain growth and enhance grain boundary strengthening effect. The TI70-Si_x alloys strengthened by the two-scale silicides exhibited remarkable strength enhancement not only at ambient temperature but also at high temperatures. The compressive yield and fracture strengths of the TI70-Si₄ alloy were increased to 1550.4 MPa and 2002.5 MPa at ambient temperature. Moreover, the TI70-Si₄ alloy exhibited ultrahigh yield strengths of 1048 MPa and 437 MPa at 600 °C and 800 °C, which were increased by 61.1% and 111.2% compared with TI70 alloy, respectively. The superior strengths can be mainly attributed to the coordinated strengthening mechanisms of two-scale silicide reinforcements and novel network microstructure.