Analysing size and shape of internal processing defects within selective laser melted aluminium alloy using x-ray micro computed tomography

Metallic components produced by additive manufacturing (AM) processes, including selective laser melting (SLM), have largely been limited to non-critical applications due to a lack of understanding of mechanical behaviour and microstructural quality. The internal micro porosity of parts produced by SLM is governed by feedstock (powdered) material properties, scanning strategy and a number of processing parameters i.e. laser power, speed of scan etc. Traditionally cast aluminium alloys such as AlSi10Mg are extensively used in automotive and aerospace applications and are widely considered as candidates for SLM. However, high reflectivity and thermal conductivity make their processing by laser especially challenging. In order to fully understand the influence of key processing parameters on the internal microstructure of SLM’d AlSi10Mg, it is necessary to categorise pore size and shape morphology in 3D. In the current work, AlSi10Mg alloy samples were manufactured by SLM using 30 unique combinations of laser power (150, 250, 350W), scanning speed (500, 1500, 2500mm/s), hatch spacing (0.3, 0.5, 0.7mm) and layer thickness (30, 60μm), covering a range of very low (68.64%) to very high (99.78%) densifications. Internal processing defects (pores) were analysed using high resolution X-ray micro computed tomography (XμCT). The influence of processing parameters on 3D porosity % and pore size/shape distribution was evaluated.