Fabrication of Intermetallic Compounds by Spark Plasma Sintering

The characteristics of spark plasma sintering, a new method of powder processing, were investigated. Four systems of intermetallic compounds—Ti-Al, Ti-Al-Cr, Mo-Si, and Mo-Si-Nb—were fabricated, and the formation process of compounds, the formed phases, and the microstructure of samples were observed. During the sintering of all the compositions of mixed powders, most of the compounds were formed by combustion reaction which occurred at almost the same temperature as the conventional combustion reaction temperature. The fabricated samples were well densified, however, the relative densities of the Mo-Si samples were lower than the Ti-Al samples. Ultrasonic images show that no internal defects were found in any sample and the grain size became finer with the increase in the Cr content in the Ti-Al system and Nb content in the Mo-Si system. The formed phases of Ti:Al=1:1 composition samples were TiAl and Ti₃Al phases, and Ti-Al added Cr samples consisted of TiAl, Ti₃Al, Cr₂Al, and Cr₉Al₁₇ phases. The sample synthesized with Mo:Si=1:2 mixed powders had only MoSi₂ phases, and Mo-Si samples with added Nb consisted of four phases: MoSi₂ with a small amount of Mo₅Si₃ phases in the matrix and Nb₅Si₃ with unreacted Nb for dispersed phases.