Enhancing the strength of AlCrFeNi HEAs via tailoring Aluminum content and optimal aging treatment

Abstract In this work, AlxCrFeNi (x = 0, 0.5, 1.0) high-entropy alloys (HEAs) were designed by introducing a high atomic radius element Al. And for x = 1.0 quaternary HEAs with equal molar ratios were studied at various aging temperatures. The microstructural evolution and its effect on mechanical properties were discussed. The results suggested that the addition of Al promoted the transition from face centered cubic (FCC) to body centered cubic (BCC) phase, in which the spherical Al-rich and Ni-rich BCC nanoparticles were dispersed in BCC. Addition of Al optimized the brittle ternary CrFeNi HEA’s shortcomings, which have high plasticity and poor strength. Besides, the results showed that the transformation of BCC to B2 phase was promoted via increasing aging temperatures. The B2 phase in the mesh structure and short rod structure was Al-rich and Ni-rich. When Al content increased to 0.5 and 1.0, the compressive yield strength increased to 1338.07 MPa and 1079.03 MPa, respectively. While the elongation remained at 15%~20%. The Vickers hardness enhanced from 147.31 HV (x = 0) to 247.76 HV (x = 1.0). When the aging temperature reached 600℃, the compressive ultimate strength and Vickers hardness increased by 165.84 MPa and 218.04 HV compared with as-cast HEAs, respectively. The series of HEAs were evaluated for the correlation between microstructure and mechanical properties.