Influence of Mechanical Alloying and Sintering Temperature on the Microstructure and Mechanical Properties of a Ti-22Al-25Nb Alloy

In this research, a fine-grained Ti-22Al-25Nb (at.%) alloy was fabricated from the powders of Ti, Al and Nb by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The effects of MA and SPS parameters on the microstructure, micro-hardness and tribological properties of the sintered compacts were investigated and discussed. The single phase of (Ti, Al, Nb) bcc solid solution with the chemical composition of Ti-22Al-25Nb was produced by MA for 5-20 h and the rotation speed of 500 rpm. The mechanically alloyed powders for 5, 10, 15 and 20 h were subsequently consolidated by SPS at the temperature range of 1000-1300 degrees C for 60 min, respectively, followed by furnace cooling. The microstructures from the sintered compacts showed that the fine equiaxed B2 phase, the lamellar or equiaxed O phase, and the equiaxed alpha(2) phase were present in all the sintered compacts. The highest micro-hardness value of 1840 HV0.3 and the smallest wear rate of 1.59 x 10(-3) mm(3)/m were exhibited in the Ti-22Al-25Nb alloy sintered at 1100 degrees C/60 min/50 MPa.