Enhanced strength and ductility of Al0.9CoCrNi2.1 eutectic high entropy alloy by thermomechanical processing

Abstract

Eutectic high entropy alloys (EHEAs) composed of soft face centered cubic (FCC) phase and hard body centered cubic (BCC) phases usually exhibit perfect combination of good tensile ductility and high fracture strength. Surprisingly, we reveal in this study that a new FCC(L12)/BCC(B2)-structured Al0.9CoCrNi2.1 EHEA shows inferior tensile properties with yield strength of 645 MPa, fracture strength of 1033 MPa and total elongation of merely 6.9%. A careful study of the deformation behavior reveals that the imperfect orientation relationship lead to extensive cleavage fracture and the consequent poor ductility. After thermomechanical treatment, a balanced and greatly enhanced tensile properties (yield strength of 820 MPa, fracture strength of 1400 MPa and total elongation of 11.6%) were achieved. The abnormal simultaneous enhancement for strength and ductility is resulted from the synchronous deformation of L12 and B2 phases. The current work presents a successfully demonstration of using thermomechanical processing to improve inferior mechanical properties of some lamellar eutectic alloys.