Effects of TiC Addition on Directionally Solidified Microstructure of Ti6Al4V

Abstract

In this study, the effects of TiC particles as the heterogeneous nucleus on the microstructure of directionally solidified Ti6Al4V were investigated. Ti6Al4V powder containing 0.0, 0.3, 1.0, and 2.0 vol pct TiC particles in a Ti6Al4V sheath was melted and directionally solidified with a floating zone melting method. In this process, the temperature gradient G was approximately 12 K/mm, and the solidification rate R was 15 mm/min. The mean size of prior β grains decreased with increasing TiC addition. In samples containing TiC particles, some grains had an aspect ratio lower than 1. This indicated that TiC particles acted as the heterogeneous nucleus and generated fine and equiaxed prior β grains. Although the many TiC particles melted into molten Ti6Al4V and the excessively melted carbon from TiC particles precipitated as Ti2C, residual TiC particles acted as a heterogeneous nucleus.