Powder sheet additive manufacturing of multi-material structures: Experimental and computational characterizations

Selective laser melting (SLM) of multi-material structures (MMS) is of significance because it allows for bespoke structural innovation and high-accuracy process tailoring. However, most of the currently developed loose powder-based SLM techniques for MMS are limited by the long changeover time and potential crosscontamination between materials. To address these issues, a novel Metal Additive Manufacturing using Powder Sheets (MAPS) technique is proposed for printing MMS within a single process. It utilizes flexible powder sheets as the feedstock material, which are composed of metal powder-polymer binder composites. The printability of MMS by MAPS is assessed through the fabrication of three-phase SS304-IN718-SS304 composites with increased geometric dimensions on the SS316 baseplates. The effects of part size on the evolution of the meltpool morphology and the formation of defects during MAPS are investigated by experimental characterizations and computational modeling. The results show that when fabricating larger MMS, the use of a longer scanvector easily leads to defects such as lack-of-fusion porosity, balling and cracks. This is due to the longer duration of inter-hatch cooling time, the reduced amount of thermal accumulation and the higher degree of residual stresses. By adopting an island scanning strategy, a defect-free large-size MMS with variations of chemical composition, microstructure and microhardness is successfully printed by MAPS. The proposed MAPS method offers a new solution for producing high-quality MMS.