Fabrication of a high strength and ductility Ti‒22Al‒25Nb alloy from high energy ball-milled powder by spark plasma sintering

A high strength and ductility Ti‒22Al‒25Nb alloy was fabricated from high energy ball-milled powder by spark plasma sintering. The pre-alloyed powder with a normal composition (at %) of 53 Ti, 22 Al and 25 Nb was firstly ball-milled for different milling times, and subsequently consolidated by spark plasma sintering. The effects of ball-milling time on the microstructure and mechanical properties of the ball-milled powder and sintered compact were investigated. The Ti‒22Al‒25Nb alloy sintered by SPS at 950 °C for 10 min under a pressure of 50 MPa from the ball-milled powder showed the microstructure with a large amount of ultrafine/nano O-phase. The best balance of tensile properties was exhibited in the Ti‒22Al‒25Nb alloy sintered from the ball-milled powder for 20 h; the yield strength, the tensile strength and the elongation to failure were 1092 MPa, 1105 MPa and 9.4% at room temperature respectively, exceeding other coarse grain Ti‒22Al‒25Nb alloys fabricated by other powder metallurgy methods in the comprehensive tensile property. The precipitation of secondary phase, the grain refinement and the change of residual dislocation density in the sintered alloy directly affected the tensile properties of the sintered alloy.