Functionally graded material via L-PBF: characterisation of multi-material junction between steels (AISI 316L/16MnCr5), copper (CuCrZr) and aluminium alloys (Al-Sc/AlSi10Mg)

Amongst Additive Manufacturing (AM) processes, Powder Bed Fusion (PBF) technologies represent one of the most promising production methods for polymers and metals, and the laser-based systems are certainly the technology that currently guarantee the production of metal parts with complex geometries, shapes, and mechanical properties comparable to those of parts produced using traditional methods. A functionally graded material (FGM) or a multi-material (MM) component can be advantageously produced with several processes and laser-powder bed fusion (L-PBF) is one of the metal-based process for their production and design. In this scenario, the paper proposes a procedure to manufacture FGM or MM parts with standard L-PBF machines, that is equipped with only one powder deposition system, using the 2D multi-material approach, where the material transition occurs between the layers with a material change along the building direction. Joints between materials of common interest, such as AISI 316L & CuCrZr alloy, AISI 316L & 16MnCr5 steel, and Al-Sc & AlSi10Mg alloy, were considered. The joints were analysed by means of metallographic investigation, neutron tomography (NT) analysis and tensile tests. The results of metallographic and tomography analyses highlight the continuity of joints establishing the possibility and the effectiveness to manufacture FGM or MM. Also, the tensile tests showed interesting results, demonstrating that the mechanical properties of the joint depend on the bulk alloy properties and on the internal structural integrity.