Microstructure and mechanical properties of Al-12Ti-6Nb prepared by mechanical alloying

An alloy Al-12wt.% Ti-6wt.% Nb was prepared by mechanical alloying (MA) process and its microstructure, mechanical properties and thermal stability were investigated. It was shown that the MA Al-12Ti-6Nb is an Al matrix composite with uniformly distributed intermetallic Al₃Ti dispersoids and single phase Nb flakes as well as fine equiaxed Al₂O₃ and rod-shaped Al₄C₃ phases. In most of the Al₃Ti particles, especially the larger ones, island-shaped α-Ti cores are normally retained. After exposure at 550°C in air for 200 h, the Al₃Ti dispersoids coarsen slowly and their α-Ti cores disappear, while the single phase Nb remains. Compared with the MA Al-12Ti fabricated in the same way, the MA Al-12Ti-6Nb shows much more excellent mechanical properties and thermal stability, which can be attributed to the more effective reinforcement of Al₃Ti dispersoids and Nb flakes due to the alleviation of their thermal expansion mismatch with the Al matrix by the addition of Nb.