Effect of warm-rolling on microstructure and superior mechanical properties of a cost-effective AlCrFe2Ni2 high entropy alloy

Abstract

The possibility of tailoring microstructure and tensile properties of a cobalt-free cost-effective (FCC+B2) AlCrFe2Ni2 high entropy alloys (HEA) was explored in this work. For this purpose, the HEA was warm-rolled at 400 °C, 600 °C, and 750 °C to 90% reduction in thickness and further annealed at different temperatures. The increasing warm-rolling reduction resulted in progressive alignment and microstructural refinement. The HEA warm-rolled at 400 °C revealed a continuous nanoscale lamellar structure as opposed to disrupted and segmented lamellae in the HEA warm-rolled at 600 °C and 750 °C. The BCC fraction increased remarkably after warm-rolling at different temperatures due to the increased stability of the BCC phase. Annealing resulted in transformation to microduplex structures and restoration of the FCC fraction. However, the HEA warm-rolled at 400 °C and annealed at 800 °C showed the development of a heterogeneous microstructure with retained lamellar and partially transformed microduplex regions. The heterogeneous lamellar microstructure resulted in simultaneous improvement in strength and ductility with a yield strength of ∼ 921 MPa and elongation of ∼23%. Thus, the HEA outperformed other cobalt-free HEAs from an integrated cost-performance comparison. Microstructural analysis of the broken tensile specimen indicated that the soft domains were considerably strain-hardened in the presence of the hard domains, leading to synergistic improvement in strength and ductility in the heterostructured HEA.