Effects of hot isostatic pressing and internal porosity on the performance of selective laser melted AlSi10Mg alloys

We herein report the preparation of AlSi10Mg alloys with a range of porosities by selective laser melting (SLM) and subsequent hot isostatic pressing (HIP). The microstructures and mechanical properties of the resulting alloys were then investigated, and the influence of the internal porosity on the mechanical properties was investigated. Under the optimum laser irradiation conditions, the tensile strength of the alloy was very high; however, this tensile strength decreased with increasing the internal porosity. Following HIP, both the proof and tensile strengths decreased significantly due to drastic changes in the microstructures, i.e., the fine dendritic cell microstructure changed to granular precipitated Si phases. In addition, the initial porosity had a relatively small effect on the proof and tensile strengths and these strengths were comparable for all materials. In contrast, the ductility of the alloy improved significantly after HIP; however, it deteriorated as the initial porosity was increased. This was accounted for by the fact that HIP treatment was not really effective for eliminating the internal pores in the SLM AlSi10Mg alloy. Therefore, the reduction of internal pores by the optimization of laser irradiation conditions is essential in the fabrication of SLM aluminum alloys.