A Study on Reaction Sintering of TiC Dispersed Ti-6Al-4V Alloy by SPS

Abstract

To improve the strength and wear resistance of Ti-6Al-4V alloy, which is widely used as a useful Ti alloy, a Ti-6Al-4V powder mixture was mechanically blended with Mo2C powder by the planet type rotating ball milling, and TiC dispersed Ti-6Al-4V alloy was produced by reaction sintering using SPS. The results of a study on the relationship between the structures and mechanical properties of this alloy prepared under various SPS conditions showed the following. When the raw powder of the Ti-6Al-4V alloy was mixed and stirred with 5 vol% Mo2C powder, the SPS reaction allowed for the preparation of a high-density TiC particle-dispersed Ti-6Al-4V alloy in a short period of time. For obtaining a uniform sintered material under 50MPa of pressure, sintering conditions including a temperature of 1373K or higher and a holding time of 0.3ks or longer were required. The matrix grain size and crystallized TiC particle size were 8∼9μm and 2.5∼3μm, respectively, under these conditions, and tended to increase with increasing sintering temperature and holding time. Although the grain growth was small up to a sintering temperature of 1373K, it was significant at 1474K. The TiC particles crystallized by the sintering reaction were effective in preventing the coarsening of the matrix structure and improving the yield stress and wear resistance. The additive material, Mo2C, on the other hand, caused a large reduction in the β-transformation temperature and an increase in the volume fraction of the β phase, leading to an effective improvement in ductility.