Microstructure and mechanical properties of a Ti−22Al−25Nb alloy fabricated from elemental powders by mechanical alloying and spark plasma sintering

This study deals with the fabrication of a fine-grained Ti−22Al−25Nb alloy from elemental powders by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The effect of SPS parameters on the microstructure and mechanical properties of sintered compacts was investigated and discussed. The (Ti, Al, Nb) bcc solid solution with a chemical composition of Ti−22Al−25Nb was produced by MA for 40 h with a rotation speed of 400 rpm, and subsequently consolidated by SPS at a temperature range of 950–1300 °C for 5, 7 and 10 min, respectively, followed by furnace cooling. The sintered compact showed the microstructure consisting of fine equiaxed B2 grains, fine O-phases with a lath shape or an equiaxed shape, ultrafine acicular O-phases inside the B2 grains, and ultrafine equiaxed α ₂ -phases along the rim of B2 grains. The best combination of mechanical properties was exhibited in the Ti−22Al−25Nb alloy sintered at 1200 °C/10 min/35 MPa; the yield strength and the fracture strain were 1652 MPa and 32.2% at room temperature, and 1163 MPa and 56.7% at 650 °C, respectively.