Ti-Si 및 Ti-Fe-Si 주조합금의 열간정수압 성형에 의한 티타늄 실리사이드의 형성과 결정학적 특성

The silicon addition in the titanium alloys yields the solid solution and titanium silicides. The morphology and distribution of the titanium silicides depend upon the alloy chemistry or the heat treatment condition, and play an important role in improving the mechanical properties of the alloys. In this study, the morphology, formation process, and crystallographic characteristics of the titanium silicides in the Ti-Fe-Si alloy system were studied. Three types of silicides were found in the alloys; (1) interconnected chain-like silicides at grain boundary, (2) coarse silicides over 1 ㎛, (3) fine silicides less than 0.2 ㎛. Ti_3Si was dominant in cast + HIP condition while Ti_5Si_3 was dominant in as-cast state. It is recognized that Ti_5Si_3 → Ti_3Si transition occurred by the peritectoid reaction and it may be promoted by pressure during HIP. However, in the case of the fine silicides, Ti_3Si and Ti_5Si_3 were found simultaneously even after HIP. Such a fine silicide was found to have crystallographic orientation relationship with β matrix.