Joint enhancement in LDED joining SLM-fabricated AlSi10Mg: A combined strategy based on ultrasonic vibration assistance, filling material and heat treatment

The high-performance joining of selective laser melted aluminum alloy by laser direct energy deposition presents a significant challenge owing to the obvious interfacial micro-performance valley, pores and microstructural differences between the joint region and base. A combined strategy based on three aspects is adopted, which includes ultrasonic vibration assistance (UVA), filling material and heat treatment. The joint microstructure evolution, defect distribution, microhardness and tensile performance of the different strategies were discussed in detail. The results showed that the joining of samples with UVA and changing the filling material strategy improved the microhardness of most areas in the joint and eliminated the pores distributed at the interface. However, the decrease in the interfacial microhardness mainly caused by eutectic silicon aggregation at the fusion line still restricted the joint strength. Fortunately, adding a post T6 heat treatment could significantly improve the weakness in the interface performance. For the high-performance laser deposition energy joining of SLM-built AlSi10Mg, each of the three regulation aspects is essential. The combined strategy based on three aspects can realize that the ultimate tensile strength of the joining samples increased to a maximum of 303 MPa, and the elongation improved to 5.7%, which was closely related to the formation of nanoscale (AlₓSi₁₋ₓ)₃(Sc,Zr) precipitates, nanoscale Si precipitates, Mg solution strengthening and low porosity. Our study offers a novel method for future high-strength welding of SLMed aluminum and the fabrication of large-sized parts via a hybrid additive manufacturing process. • A novel combined strategy has been proposed for synchronously manipulating the porosity and microstructure of joint region. • The pore elimination and strengthening mechanism of joint is revealed in detail. • The post T6 heat treatment significantly improved the interfacial mechanical performance. • The high-performance joint with average tensile strength of 303 MPa could reach SLMed AlSi10Mg base material.