Effect of solution and aging treatments on the microstructure and mechanical properties of dual-phase high-entropy alloy prepared by laser-powder bed fusion using AlSi10Mg and FeCoCrNi powders

Using the insufficient diffusion of the elements forming the BCC phase under rapid solidification, a dual-phase Si - containing Al0.4CoCrFeNi high-entropy alloy (HEA) with a body-centered cubic (BCC) phase content of approximately 13 % and good mechanical performance was prepared by laser-powder bed fusion using AlSi10Mg and FeCoCrNi mixing powders. The effect of aging treatment with and without the preceding solution treatment on the microstructure and mechanical properties is addressed. Under direct aging, a large number of nano sigma and face-centered cubic (FCC) phases are formed within the BCC phase, and the spherical L12 phase and dislocation cellular substructure coexist inside the FCC grains. However, under solution aging, the BCC phase is separated by a newly generated FCC phase and shows a sieve-like shape with the sigma phase embedded into the phase boundary, and the L12 phase is precipitated in a wave-like shape inside FCC grains without dislocations. Thus, direct aging can rapidly improve the strength of the as-built alloy; however, the plasticity decreases significantly. By contrast, solution aging improves strength while retaining considerable plasticity. Specifically, solution aging treatment at 1200 degrees C/1 h + 650 degrees C/50 h simultaneously improved the strength and plasticity of the as-built alloy. Further- more, the solution aging sample at 1200 degrees C/1 h + 650 degrees C/100 h achieved a synergistic increase in strength and plasticity compared with all of the direct-aged samples. This work proposes a new concept for preparing het- erogeneous alloys with a high second-phase content using a low content of phase-forming elements and also provides guidance for the post-treatment performance regulation of dual-phase HEAs.