Selective Laser Melting to Manufacture “In Situ” Metal Matrix Composites: A Review

After a brief introduction on selective laser melting (SLM) and “ex situ” manufacture of metal matrix composites (MMCs), this paper reviews the capacities and benefits of SLM to activate and control various “in situ” reactions during fabrication of 3D parts. It introduces several systems (such as Al/Fe2O3, AlSi10Mg/SiC, Al/ZnO, Ti/C, Ti/SiC, Ti/Si3N4, Ti/Mo2C, Fe/SiC, etc.) used to manufacture Al‐based, Ti‐based, and steel‐based “in situ” MMCs. Then, it illustrates the novel microstructural characteristics of these SLM‐made “in situ” MMCs for different cases, as they may appear from nano‐particles to nano‐whiskers and dendritic reinforcements homogeneously distributed in a metal matrix. It also focuses on SLM associated “in situ” mechanisms, explaining how an “in situ” reaction propagates based on “decomposition, diffusion, and reformation” and how the growth mechanisms turn into different morphologies such as rounded particles, whiskers, or polygonal block shapes. The influence of various SLM parameters (such as energy density, laser power/speed, powder layer thickness, and the size of initial powder particles) and the SLM “in situ” challenges are also discussed. This paper describes the advancements to manufacture metal matrix composites (MMCs) using selective laser melting (SLM) from reactive powders. Based on various metal‐based powder systems, it discusses how different novel microstructures and properties can appear in the “in situ” made MMCs. As an example, the shown figure illustrates the propagation of “in situ” products throughout an Al/Fe2O3 powder mixture.