Seed를 이용한 일방향 응고법에 의한 TiAl합금의 층상경계방향제어

Abstract

The thermal stability of the lamellar microstructure and the orientation control of the lamellar microstructure in a cast TiAl alloys with Mo and C were investigated. The lamellar stability of the seed material up to the melting temperature is important in the orientation control of the lamellar microstructure by the directional solidification. First, the partial liquidus surface was constructed for TiAl-C ternary and TiAl-1.5Mo-C quaternary systems. The lamellar stability was determined by quickly heating specimens to a temperature just below the melting temperature, holding, and then cooling to room temperature. Ti-46Al-1.5Mo-0.2C alloy was found to be a promising composition as a seed materials and ingots with a lamellar microstructure aligned along the growth direction were successfully grown by directional solidification process using the seed alloy. From the result of tensile and compression tests, directionally solidified Ti-46Al-1.5Mo-0.2C (at.%) ingots were found to exhibit a high yield stress together with a reasonably good tensile elongation at room temperature and a high compression stress up to 1000℃.