Effect of heat treatment on the microstructure and mechanical property of W/316L multi-material fabricated by selective laser melting

W/316L multi-materials can realize the function of W as the plasma facing material and 316 L as the structural material in nuclear fusion reactors. In this study, well-bonded W/316L multi-material was firstly manufactured by selective laser melting (SLM) and the influence of heat treatment on the microstructure and mechanical property of W/316L was investigated. Results showed that the pores and cracks located at the bonding region could be reduced significantly by heat treatment at 1200 oC for 1 h. There was an obvious static recrystallization phenomenon of equiaxed sub-crystals among the bonding region and the existence of secondary Fe3W3C, Fe6W6C intermetallic compounds initiated from primary Fe2W and Fe7W6 matrix. In terms of mechanical properties, 22% increase in micro-hardness obtained at the W/316L bonding region, as well as an increase from 5.2% to 22.8% of the elongation after heat treatment was attributed to the precipitation of more secondary Fe3W3C, Fe6W6 phases, which introduced more nucleation sites and limited the slip of dislocations. This work provides a novel approach to fabricate and optimize W/316L multi-material.