Directed energy deposition of aluminium bronze onto H13 steel-microstructure in multi-material additive manufacturing

Multi-material additive manufacturing has over the years had increasing interest due to the possibility of combining attributes of different alloys to create parts with tailored properties. This study investigates the combination of aluminium bronze and AISI H13 tool steel, through laser-based directed energy deposition with powder feedstock and focuses on the microstructure near the bonding interface. Combining such materials can utilize the thermal properties of bronze and the mechanical properties of tool steel. The characterization was performed using a variety of techniques, including optical– and secondary electron microscopy, atom probe tomography, and X-ray microtomography. The deposition of bronze onto steel resulted in an interface nearly free of imperfections between steel and bronze, as well as a mixing zone where nearly spherical iron-rich particles were suspended in a bronze matrix. The miscibility gap in the iron-copper liquid primarily caused the formation of these spherical iron-rich particles, and the separation of elements in the liquid phase is believed to prevent the formation of intermetallic particles. Additionally, the region around the mixing zone exhibited increased hardness, approximately 1 mm above and below the bronze-steel interface, compared to the bulk bronze and steel.