Effects of substrate surface treatments on hybrid manufacturing of AlSi7Mg using die casting and selective laser melting

To balance the manufacturing cost and customizability of automotive parts, a hybrid manufacturing pro-cess combining die-casting and selective laser melting (SLM) is proposed: starting with a conventional cast substrate, SLM is utilized to add additional geometric elements on top of it. For this hybrid process, the first priority is to prepare a substrate surface suitable for the subsequent SLM addition of the top-on elements. In this study, the original cast surface of AlSi7Mg was processed by sandblasting, wire electro-discharge machining, and laser remelting, respectively. Then, additional AlSi7Mg components were built on both the original cast and treated surfaces through SLM. After hybrid builds, these surfaces and re-sultant interfaces were examined by optical and scanning electron microscopes. Results indicate that the defect-free metallurgical joint between the cast and additively added parts can be formed on all surfaces except for the one processed by electro-discharge machining. The observed epitaxial grain growth cross-ing the interface implies a strong connection between the cast and the SLMed component. Despite these benefits, also mismatches in microstructure, residual stress level and element distribution between the two parts are identified. After a comprehensive assessment, laser remelting with no additional machining is recommended as the optimal surface treatment preceding SLM fabrication, because of its user-friendly operation, low cost, and high industrial feasibility.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.