The reaction process of Ti and Ni during sintering process of the Ti-50 at%Ni binary mixed powder compacts was investigated by the model experiment using the synthetic compacts of φ300 μm Ti wire and carbonyl Ni powders, and also the dimensional changes were examined by the dilatometric method both in the press direction and that perpendicular to it.
The results obtained are as follows: The width of growth layers of intermetallic compounds, such as Ti₂Ni, TiNi and TiNi₃ produced in the press direction by the interdiffusion between Ti and Ni during sintering was thick, while in the direction perpendicular to it, it was thin, and some pores which are thought to he one of the main factors for the expanding phenomenon were observed in the Ni side of the interface between Ti wire and carbonyl Ni powders. On the other hand, the anisotropy of dimensional change was observed by the dilatometric method; i.e., the continuous shrinkage in the press direction and the great expansion especially in the temperatures higher than 955°C of eutectic reaction in the direction perpendicular to it. Judging from the above mentioned results of model experiment, it was confirmed that this anisotropy of dimensional change was deeply related to (1) the contracting phenomenon due to the appearance of thick layer of the intermetallic compounds in the press direction, and (2) the expanding phenomenon due to a reaction between the eutectic liquid and the intermetallic compounds being greater in the direction perpendicular to it where the width of Ti₂Ni phase contacting with the eutectic liquid is thin.