Additive friction stir deposition of multi-layer aluminum-silicon carbide metal matrix composites

• Successful AFSD using commercial 25 vol.% SiC-reinforced aluminum MMC feedstock • Complex, heterogeneous intermixing of baseplate material and deposited MMC • AFSD process results in some SiC fragmentation and minor decrease in particle size • Heat treatment after deposition fully recovers hardness of MMC and baseplate Aluminum metal matrix composites (MMCs) possess good strength and stiffness combined with low density, making them attractive in a variety of applications. Additive friction stir deposition (AFSD) is a relatively new, solid state metal additive manufacturing process that has high potential as a forming route for MMCs of complex shape. However, little work has been done to investigate how AFSD affects microstructure and properties of conventional MMCs. In this work, aluminum-silicon carbide (Al-SiC) MMC extruded plate was used as feedstock for AFSD to create a five-layer deposit of an Al-SiC MMC for characterization. Microstructure, particle size distribution, and hardness were evaluated in the as-deposited condition while hardness recovery was investigated with post-deposition solution and aging heat treatments. The deposited MMC revealed complex, macroscale mixing behavior, mild fragmentation of the SiC particles, and uniform particle size distribution and dispersion across MMC regions of the deposit. Solution and aging heat treatment restored the hardness of the deposited MMC to that of the as-received feedstock. This work suggests AFSD is a promising route for producing complex MMC parts with similar or better properties to those produced by traditional processes.