Formation of La-modified L12-Al3Ti by mechanical alloying and annealing

DO22-Al3Ti can be transformed into the related cubic L1(2) structure, with more slip systems, by the addition of ternary elements, such as the rare earth Lanthanum. It is believed that combined processing by mechanical alloying and annealing is conducive to the structural evolution and crystal growth. Appropriate and economical processing parameters were determined as: milling time of 40 h, annealing temperature of 750 degrees C and annealing time of fine and uniform 40-60 min. With increased milling time fine and uniform particls which originally possess a flake-like morphology, are produced. The Vickers hardness of the as-milled Al-Ti and Al-Ti-La powders increases rapidly at the initial milling stage, then increases slowly at final stage due to lattice distortion and solid solution strengthening. However, the Vickers hardness of the two materials decreases with increased of annealing time. The Vickers hardness of the Al-Ti powders is higher than that of the AI-Ti-La powders. (c) 2007 Elsevier Inc. All rights reserved.