Influence of mechanical alloying on the microstructure and mechanical properties of powder metallurgy Ti2AlNb-based alloy

Abstract

A fine grained Ti2AlNb-based alloy with a high strength was fabricated from elemental powders by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The effects of MA parameters on the microstructure and mechanical properties of the mechanically alloyed powder and sintered compacts were investigated. The single phase of (Ti, Al, Nb) bcc solid solution with a normal composition (mole fraction, %) of 53 Ti, 22 Al and 25 Nb was produced by MA for 40h/400rpm. The mechanically alloyed powder was subsequently synthesized by SPS at 1150°C/10min/35MPa followed by furnace cooling. The microstructure of the sintered alloy consisted of fine grained B2-matrix, ultrafine acicular O-phase inside B2-matrix, and ultrafine equiaxed α2-phases along the rim of B2-matrix. The yield strength and ultimate strength of the alloy sintered from the 40h mechanically alloyed powder were 1644MPa and 2542MPa in the compression test, respectively. Meanwhile, the strains to failure at room temperature and 650°C were 31.3% and 55.3%, respectively.