Micro structure 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 A12O3 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.