Thermal and mechanical properties of commercial-purity aluminum fabricated using selective laser melting

Optimum laser irradiation conditions for densifying commercial-purity aluminum fabricated using selective laser melting (SLM) were studied using an SLM machine equipped with a 400 W Yb fiber laser. SLM specimens with a relative density of 99.7% could be obtained. The microstructures and the thermal and mechanical properties of dense SLM specimens fabricated under the optimum laser irradiation conditions were investigated. The as-fabricated SLM specimens showed granular microstructures of aluminum, silicon, and/or iron oxides dispersed finely (～0.3 µm) due to the rapid solidification by the laser irradiation. The mechanical properties were thus confirmed to be excellent (ultimate tensile strength, 110 MPa; yield strength, 90 MPa; breaking elongation, 30%). The thermal conductivity of the SLM specimen, meanwhile, was about 200 W/m·K, which was inferior to that of wrought commercial-purity aluminum (230 W/m·K). The effects of heat treatment (annealing) on the properties of the SLM specimens were also investigated. The thermal conductivity of an SLM specimen annealed at 450°C for 10 min increased to the same value as that of wrought commercial-purity aluminum, although the yield strength and breaking elongation were both slightly decreased.