Effect of heat treatment on microstructure and mechanical properties of a selective laser melted Cu–15Ni–8Sn alloy

Abstract

As a high strength wearproof alloy, Cu–15Ni–8Sn alloy structures were fabricated by selective laser melting (SLM), while they possessed poor mechanical properties due to the absence of precipitated phase, and thus they are on the halfway to industrial application. SLM-processed Cu–15Ni–8Sn alloy subjected to heat treatments is studied to further improve the performance. Microstructure evolutions and mechanical properties variations were investigated, and the strengthening mechanisms are discussed. SLM-processed matrix is a supersaturated solid solution with fine grains, leading to important yield strength contributions from solid solution strengthening. The incremental strength for heat-treated samples aged at 400 °C is mainly due to the DO22 ordering and the spinodal decomposition. The precipitation strengthening increased from 1.4% to above 70% after heat-treatment. Among the three aging methods, directly aging (DA) samples showed highest strength than the other two methods. The directly aged samples exhibit fine grains and high dislocation density, resulting in high grain boundary strengthening and dislocation strengthening. Moreover, direct aging treatment is an economical and environment-friendly way to improve mechanical properties of SLM-processed precipitation-hardened alloy, which is a high strength conductive elastic material.