The influence of surface roughness on the fatigue performance of selective laser melted aluminum alloy A357

As one of the most typical additive manufacturing (AM) technologies, selective laser melting (SLM) removes many of the shape restrictions that limit materials design, thereby allowing computationally optimised and high-performance structures to be directly produced and tested. Due to factors such as high reflectivity and lower absorptivity of A357 alloy powder during high temperature laser melting, issues SLM might bring are the surface roughness and defects present on the parts. In this regard, this study investigates the surface roughness - mechanical property relationship for a heat-treated aluminium alloy A357 after SLM. Via the adjustment of SLM parameters, an ultrafine microstructure can be obtained due to the fast solidification rate. Therefore, comparable or even better mechanical properties can be achieved with respect to traditional A357 casting counterparts. Meanwhile, the up-skin and down-skin conditions of the selective laser melted Al alloy are also influenced by various processing parameters, raw powder properties, as well as sample building geometry and location variation. For selective laser melted materials, a dense part with a smooth surface would be expected to correspond with a good fatigue performance for both the as-fabricated and heat treated Al alloy A357 net-shaped components.

Keywords: Al-Si alloys; microstructure; heat treatment; mechanical properties; selective laser melting