Microstructure and Mechanical Properties of The L12/L21 Two-Phase Alloys In The Quaternary Co-Al-Ni-Ti System

An attempt is made to develop a two-phase alloy consisting of the Ll2 and L21(Heusler) phases in the Co–Al–Ni–Ti quaternary sytem exhibiting a high elevated temperature strength as well as some room temperature ductility as a new class of heat resisting structural materials. The idea behind this approach is expectations for the L21 phase to provide high elevated temperature strength, whereas the Ll2 phase provides some room temperature ductility. Compositional optimization in the room temperature ductility of the Ll2 (Co,Ni)3(Al,Ti) is first carried out and then, based on the result, several L12/L21 two phase alloys are designed. It is found that a few to several per cent room temperature bend ductility is obtained in such two-phase alloys.