Metal matrix composites processed by laser additive manufacturing: microstructure and properties

Metal matrix composites (MMCs) offer the possibility to enhance the mechanical properties of metallic materials and develop new functionalities, as self-lubrication or self-cleaning. In recent years, laser additive manufacturing (AM) has imposed itself as a powerful method for the production of MMCs. MMCs may be produced in complex shapes, as coating or localized insert. The second phase of the composite may be produced in situ, i.e. by a chemical reaction during fabrication. Alternatively, the reinforcing phase may be mixed - ex situ - with the powder of the matrix, where dissolution of the second phase and interfacial reactions between the second phase and the matrix may also occur. Moreover, the extremely high cooling rates experienced during laser AM generally lead to out-of-equilibrium microstructures (chemical supersaturation and grain refinement). This chapter aims at reviewing the state-of-the-art concerning laser additive manufactured MMCs, focusing on the characterization of their complex microstructures and usage properties.