Particulate reinforced composites are expected to solve the problem of grain growth and strength reduction caused by multiple thermal cycles during additive manufacturing. In this work, TiB2/2319Al composite was fabricated by oscillating laser-arc hybrid additive manufacturing (O-LAHAM). The microstructure, mechanical properties and fracture of tensile samples were studied. The results show that TiB2/2319Al composites were composed of fine equiaxed grains due to the stirring effect of laser beam and the particle strengthening effect of TiB2. Although ultimate tensile strength (UTS) of the TiB2/2319Al composite did not increase significantly, it had a higher yield strength (YS), especially stimulated by T6 heat treatment. Compared with 2319 aluminum alloy, YS of the as-deposited and heat-treated composites was 137 MPa and 355 MPa, respectively, which increased by 19% and 10%. However, the elongation decreased significantly, which is caused by the presence of micro pores that promoted crack propagation.
Narrow gap oscillating laser welding of 6061/2024 dissimilar aluminum alloys with hot wire was carried out. The effects of processing parameters on weld formation were investigated. The results show that increasing the laser power (P) and the wire current (I) can suppress the lack-of-fusion, while increasing the oscillation frequency (f) can effectively eliminate the weld porosity. Furthermore, 20mm-thick joint was fabricated with optimized process parameters and the microstructure and mechanical properties were analyzed. The weld center exhibits an equiaxed microstructure composed of α-Al matrix, eutectic on the grain boundary, and point-like precipitation phase in the grain, while the interlayer weld exhibits a gradient microstructure composed of columnar grains, coarse grains, and equiaxed grains. The joint shows good consistency in hardness and tensile properties. The highest tensile strength and elongation are 215 MPa and 9%, which are 69% and 66% of the 6061 aluminum alloy, respectively.
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