Additive friction stir deposition of Al 6061-B4C composites: Process parameters, microstructure and property correlation

Al 6061-B4C metal matrix composites were fabricated using a novel solid state additive manufacturing technique of additive friction stir deposition (AFSD). Incorporation of B4C particles into the deposit was achieved by employing hollow Al 6061 feed stock filled with B4C powder and three different AFSD tool rotational speeds (200, 300 and 400 rpm). Fabricated deposits exhibited remarkable metallurgical bonding across the substrate/deposit interface and interlayer interfaces for all tool rotational speeds, indicating a wider fabrication window. A physics based pseudo-thermo mechanical model was employed to evaluate the thermo-kinetic conditions experienced by the depositing material to correlate with the microstructural observations. Deposited layers exhibited refinement of grains to ∼10 μm from the corresponding coarse grain structure of feedstock (136 μm). The regions near the B4C particles were observed to have finer grains (