Microstructure control and tensile properties of three-phase alloys based on the E21 Co3AlC and B2 CoAl

To investigate tensile mechanical behavior, tensile tests were conducted at room temperature and 1273 K on three-phase alloys consisting of the E2₁ Co₃AlC, B2 CoAl and (Co) primary solid solution. The alloy containing a large volume fraction of E2₁ phase exhibits excellent ductility, exceeding 5% plastic strain at room temperature, while the alloy with a considerable amount of coarse B2 phase particles shows zero ductility. In this study, microstructure control was used to improve the ambient temperature ductility of the E2₁/B2/(Co) three-phase alloys. Hot forging and subsequent heat treatments were performed aiming at eliminating solidification defects and minimizing the heterogeneity of the as-cast microstructure. These thermomechanical treatments together with compositional control effectively improve the ductility of the E2₁/B2/(Co) three-phase alloys at ambient temperature and 1273 K.