Processing optimisation, mechanical properties and microstructural evolution during selective laser melting of Cu-15Sn high-tin bronze

Abstract

Selective laser melting (SLM), as a novel additive manufacturing technique, has attracted increasing attention in copper alloys. In this research, to investigate forming processing and attendant mechanical properties of high-tin bronze in SLM, a statistical relationship between processing parameters (laser power, scanning speed and hatch space) and density of Cu-15Sn bronze in SLM was established using an experimental approach with response surface method and analysis of variance. As such, nearly fully-dense SLM Cu-15Sn bronze specimens were firstly manufactured whose reasonable microstructural evolution and mechanical properties were investigated before and after annealing and compared with QSn15-1-1 (GB/T 5231-2012) drawing specimens. It is found that the SLM Cu-15Sn specimens present the significantly fine grain microstructures that consist of cellular and dendritic structures. The ultimate tensile strength varies from ~661 MPa to ~545 MPa, the elongation at break from ~7.4% to ＞20% and the Vickers hardness ranges from ~212 HV 0.3 to ~168 HV 0.3 for SLM Cu-15Sn specimens after annealing, which are generally superior to those of QSn15-1-1 specimens. In addition, it has been proposed that the dominated strengthening mechanism of SLM Cu-15Sn parts has transformed from fine-grain to solid solution strengthening after annealing.