Investigation on reducing distortion by preheating during manufacture of aluminum components using selective laser melting

Abstract

The additive manufacturing process selective laser melting (SLM) can be used to directly produce functional components made out of metal. During the construction process, however, thermally induced residual stress occurs due to the layered build-up and the local input of energy by means of a focused laser beam, which can lead to distortion of the component or sections of the component itself. Normally, distortion is prevented due to supporting structures between the component and the substrate plate. It is not always possible, however, to provide all the areas of a component with supporting structures or to remove them later, depending on how complex the geometry or how accessible the structures are. When the substrate plate is heated during the construction process, the distortion can be reduced or eliminated entirely. Nonetheless, a systematic investigation of the extent to which preheating influences distortion of aluminum components has not yet been conducted. This works aims at systematically investigating the effects of preheating during SLM of aluminum components and determining an appropriate preheating temperature at which distortion practically no longer occurs. A significant reduction in distortion compared to the distortion without preheating can be seen beginning at a preheating temperature of 150 °C. At a preheating temperature of 250 °C, distortion can no longer be detected within the scope of the measuring accuracy independent of the twin cantilever test geometry investigated. In addition to reducing distortion, the preheating avoids the stress-related cracks in the component, which can lead to tearing of the parts of the test geometry. With 90 HV 0.1 at a preheating temperature of 250 °C, the hardness is greater than the required minimum hardness according to DIN EN 1706 of die-cast parts from the material AlSi10Mg. From these results, it can be concluded that a preheating temperature of 250 °C is suitable for reliably manufacturing components made out of the material AlSi10Mg using SLM free of defects and for preventing distortion completely.