Effect of Nb and Nb₂O₅ additives on mechano-thermal processing of TiAl/Al₂O₃ nano-composite

In this research, TiAl matrix nano-composite with Al₂O₃ reinforcement was obtained by mechanical activation of TiO₂ and Al powder mixture and its subsequent heat treatment. Effect of Nb and/or Nb₂O₅ additions on the process was investigated. Structural changes and thermal behavior of the samples were evaluated by X-ray diffraction and differential thermal analysis, respectively. Moreover, the microstructure was characterized by transmission electron microscopy. The results confirmed the partial dissolution of Nb in Al during the milling stage in the Nb-added samples. The reaction mechanism during heat treatment in the sample without any additives was a two-stage process that was quite similar to the sample with Nb addition. However, Nb₂O₅ addition led to the progress of reaction through a single stage and with a higher rate. Both additives promoted formation of the Ti₃Al phase in the final products. The results confirmed the formation of nano-sized Al₂O₃ particles in a nano-crystalline Ti–Al matrix with a mean crystallite size of 30 nm.