A study on the microstructural evolution and strengthening mechanisms of the lightweight (Ti61Al16Cr10Nb8V5)99.6Si0.4 multi-principal alloy with excellent high-temperature mechanical properties

This study introduced a novel lightweight multi-principal alloy, (Ti₆₁Al₁₆Cr₁₀Nb₈V₅)_99.6Si_0.4 (Ti61Si0.4), characterized by its superior high-temperature mechanical properties. At room temperature, the rolled Ti61Si0.4 alloy features BCC/B2 matrix with equiaxed grains of 36 μm, accompanied by small amounts of spherical Ti₃Al phases (100–500 nm) and rod-like Ti₅Si₃ phases (0.2–2 μm). Performance testing showed that the Ti61Si0.4 alloy has density of 4.82 g/cm³, tensile strength of 1280 MPa, and fracture strain of 3.5 %. At 600 °C, 650 °C, and 700 °C, the alloy's quasi-static tensile strengths and fracture strains were measured at 920 MPa and 6.7 %, 750 MPa and 16.3 %, and 570 MPa and 45 %, respectively. Microstructural observations reveal a transformation from BCC/B2 to Ti₃Al phase beginning at 600 °C and a eutectoid transformation from BCC/B2 to Ti₃Al + TiCr₂ beginning at 650 °C. Precipitations enhance the alloy's strength through a dislocation bypass mechanism. Compression tests at strain rates from 0.001/s to 1/s between 600 °C and 700 °C demonstrate significant strain rate strengthening effects, with calculations confirming that changes in the alloy's dislocation deformation mechanism are the primary cause of this strengthening. The Arrhenius equation accurately describes the deformation behavior of the Ti61Si0.4 alloy within the 600–650 °C range. Compared to high-temperature titanium alloys, Ti61Si0.4 alloy offers significant advantages in high-temperature strength and specific strength, while also maintaining good room-temperature workability, indicating great potential for applications in aerospace fields.