Microstructural control for ductilization of multi-phase alloys based on B2 CoAl

Tensile tests were carried out on several alloys based on the B2 intermetallic compound CoAl. The alloys are multi-phase with Co primary solid solution, L12(Co,Ni)3Al, or E21Co3AlC; they were developed by the present authors and showed some room temperature ductility previously under compression testing. Also, attempts to refine the microstructure of the selected alloys were made using heat treatment and hot or cold rolling. Although no drastic improvement in room temperature ductility is observed, indications of a microstructure favorable for improved ductility are obtained. Also, it is found that some type of solidification defect causes premature failure during tensile tests, but not during compression tests, for which a cure should be sought after further improvement in the mechanical properties.