Abstract
Effect of phase change from unstable to stable phase on densification process by pressure sintering was studied using mechanically alloyed powder. Powder mixture of Ti and Si having the composition of Ti-37.5mol%Si were milled for 3600ks. The powder showed homogeneous microstructure and amorphous-like XRD profile. And also 360ks milled powder having (Ti+Si) lamella microstructure was used. Milled powders were vacuum hot pressed at constant heating rate up to 1273K with applying constant pressure of 100MPa, then kept for 10.8ks. It was observed that the sudden increase in density at the temperature range between 840K and 905K. This temperature range showed good agreement with that of the phase formation from unstable to stable phase, Ti_5Si_3. From experiments to measure the thermal expansion of amorphous and elemental compacts and to consider the densification behaviors of heat treated powders, it is presumed that the enhancement of densification during crystallization from amorphous phase is closely related the extra ordinate deformation of amorphous material around the crystalline nucleation.
