Dual-heterostructure in selective laser melted CuCrZr alloy: Formation mechanism, deformation behavior and mechanical response

Abstract

CuCrZr alloy is considered a promising candidate for combustion chamber liners by virtue of its excellent strength and conductivity. In this study, a CuCrZr alloy fabricated by selective laser melting (SLM) and subsequently peak-aged at 500 °C for 0.5 h achieves an excellent strength-conductivity synergy. This enhancement is attributed to the synergistic effect of a heterogeneous grain structure and dual-scale precipitates. The results indicate that the as-built CuCrZr alloy exhibits a bimodal grain structure, consisting of coarse columnar grains in the melt pool centers and fine equiaxed grains in the boundary overlap regions. Simultaneously, intrinsic heat treatment during SLM leads to the formation of primary coarse Cr precipitates with incoherent phase interface. Subsequent aging promotes the precipitation of fine, coherent secondary Cr precipitates. During deformation, plastic incompatibility, arising from the preferential yielding of coarse columnar grains constrained by elastic fine equiaxed grains, creates strain gradients and geometrically necessary dislocations accumulation. The increasing low-angle grain boundaries fraction with strain helps coordinate this deformation, while the ensuing strain partitioning maintains a strain gradient that thereby drives continuous work hardening to fracture. The precipitates govern strengthening via shearing/Orowan mechanisms. The consequent microstructural evolution, from dislocation forests to final damage initiation, underpins the robust mechanical response. This integrated design yields a substantial improvement in both ultimate tensile strength (to 652.8 MPa) and electrical conductivity (to 62.3% IACS) for as-built CuCrZr alloy.