Abstract:
Ti
2AlC/Inconel 718 composites were prepared by selective laser melting (SLM) process. Three types of heat treatments were carried out on the composites, respectively: direct double aging (DA), solution double aging (SA), and homogenization+solution double aging (HSA). The effects of heat treatments on the microstructure and mechanical properties of the composites were studied. The results show that after the direct double aging heat treatment, the microstructure of the samples contains a large amount of white Laves phase precipitates. After the solution double aging treatment, a large number of needle-shaped white δ-phase precipitates are formed at the grain boundaries. Meanwhile, γ′ phases and γ″ phases are precipitated within the grains, with shapes being spherical and disc-shaped. The Laves phases in the Ti
2AlC/Inconel 718 composites after the homogenization+solution double aging treatment are significantly less than those in the samples treated with direct double aging or solution double aging. However, the precipitation of carbides increases, and most of them are distributed along the grain boundaries. After the direct double aging treatment, due to the precipitation of γ′ phases and γ″ phases, the microhardness and tensile strength are significantly improved. However, due to the increase in strength and the insufficient dissolution of the deposited Laves phases, the elongation after fracture and the contraction rate are decreased. After the solution double aging treatment and the homogenization+solution double aging treatment, the Ti
2AlC/Inconel 718 composites undergo recrystallization, which counteracts the rapid solidification microstructure obtained by SLM. Meanwhile, compared to the samples treated with direct double aging, due to the precipitation of needle-shaped δ phases at the grain boundaries, the strengthening element Nb is consumed, and the precipitation of γ″ and γ′ phases is reduced, resulting in a significant decrease in strength. The plasticity increases by 10.5%, meeting the usage standards of this material.