Effect of aging on microstructure and property of AlCoCrFeMo0.05Ni2 high entropy alloy

The effect of aging on the microstructure and property of a newly high entropy alloy (HEA) with balanced strength-ductility and good high temperature property is studied. The results show that the microstructure of AlCoCrFeMo0.05Ni2 high entropy alloy forging consists of Fe, Co rich FCC phase, Al, Ni rich BCC phase and Cr, Mo rich BCC phase. The area ratios of FCC and BCC phases are about 61% and 39%, respectively. After aged at 680 °C and 700 °C, an Al, Ni rich needle-like phase with FCC structure is precipitated in the original FCC phase; the Cr, Mo rich BCC phase grows up, aggregates at the grain boundary and forms finally block σ phase. The microstructure of the alloy aged at 700 °C is refined continuously without change in the area ratios of the Al, Ni BCC phase as the aging time prolonged. The mechanical property of the alloy aged at 680 °C for 8 h is excellent at room temperature. And the yield strength, tensile strength, and elongation are 1080 MPa, 1393 MPa, 19.5%, respectively. The elongation of the alloy aged at 700 °C for 150 h can reach up to 80% at 700 °C. [Display omitted] •AlCoCrFeMo0.05Ni2 HEA designed by our group has excellent balanced strength-ductility.•Electroslag ingot of AlCoCrFeMo0.05Ni2 HEA has been forged into φ 16 mm bar successfully.•The needle-like phase is the mainly aging strengthening phase in AlCoCrFeMo0.05Ni2 HEA.•The σ phase at the grain boundary of the aged alloy is evolved from the spherical Cr, Mo rich phase.•The high temperature ductility of the alloy increased significantly due to the ultrafined microstructure.