Feedstock preparation, microstructures and mechanical properties for laser-based additive manufacturing of steel matrix composites

Laser-based additive manufacturing (LBAM) has shown great potential in the development of new metallic materials, especially in the design and fabrication of metal matrix composites (MMCs). Steel matrix composites (SMCs) as one MMC-type, have been successfully additively manufactured with full density and good performance. This article reviews emerging studies of LBAM-fabricated SMCs, starting from the methods of feedstock preparation including respective merits and challenges. The mechanisms of phase transformation, grain growth and texture development of the steel matrix, as well as the precipitation of reinforcements during rapid solidification inherent to LBAM are demonstrated. Microstructural features of SMCs with different matrix (austenitic, martensitic, duplex and ferritic) and reinforcement types are discussed. The interrelationship between the composition and physical properties of the composite powder, microstructures and mechanical properties of SMCs are disclosed and the involved strengthening mechanisms are discussed. Lastly, conclusions and outlook focusing on emerging trends of LBAM-fabricated SMCs are presented.