Multifunctional Metal Matrix Composites by Friction Stir Additive Manufacturing

We report a class of multifunctional metal matrix composite (MMC) materials that combine structural and functional properties, potentially providing significantly improved protection against space environmental hazards, without the punishment of increasing weight and size or poor scalability. Formed by a scalable friction stir additive manufacturing (FSAM) process, these MMCs are incorporated with a high level of uniformly distributed ceramic or metallic particles at a fraction of greater than 30%. The microstructures of the metal matrices between these added particles are significantly refined by the FSAM process as well as by the presence of large amounts of the particles, e.g., interparticle space of down to less than 1 mu m in aluminum MMCs. Consequently, a combination of this high concentration of ceramic and metallic particles and the refinement of the MMC matrix by the FSAM process results in not only enhancing mechanical properties, e.g., hardness and resistance to wear but also embedding functionalities of these incorporated particles in the MMCs. These embedded functional properties can be controlled to provide effective shielding of particle radiation, improved tolerance to high temperature, increased friction force at contact surfaces, etc., which are critical to mitigate the hazards of the space environment.