Comparison of microstructures and mechanical properties of as-cast and directionally solidified Ti-47Al-1W-0.5Si alloy

Abstract

The as-cast Ti-47Al-1W-0.5Si alloys were prepared by induction skull melting (ISM) technology under argon atmosphere. Some bars were cut from as-cast ingot longitudinally and then were directionally solidified by Bridgman solidification technique. The microstructures and mechanical properties of the as-cast and directionally solidified Ti-47Al-1W-0.5Si alloy ingots with different lamellar orientations were investigated. After directional solidification, the grain boundaries were eliminated and the lamellar orientation was nearly parallel to the growth direction. The interlamellar spacing of directionally solidified samples decreased from average 1500 nm to less than 1200 nm and the interlamellar spacing was more homogeneous. In addition, the shape of Ti5Si3 transformed from short rod to strip along the growth direction, and the B2 phase disappears after directional solidification. At room temperature, the compressive yield strength of Ti-47Al-1W-0.5Si alloy increases from 573 in as-cast condition to 651 Mpa after directional solidification. The fracture mode transforms from inter-granular fracture to inter-lamellar fracture after directional solidification.