Effect of Alloying Powders on Microstructure and Mechanical Properties of Aluminum Alloy Arc Additive Manufacturing

Cold metal transfer arc additive manufacturing technique was used to produce 5356 aluminum alloy by adding refining agents to solve the problems of coarse grains and poor performance. Metallic powders (Ti, TiH, and Ti+B₄C) were used to refine the grain size and promote the mechanical properties of the alloy. The effects of refining agents on the microstructure and mechanical properties of straight wall samples (SWSs) were studied. Samples with Ti+B₄C addition had a profound impact on morphology. However, the TiH added sample revealed uneven transition between sediment layers, unstable precipitation process, unstable wall height and wall width, poor morphology, and defects. All SWSs with powder addition revealed the formation of the Al₃Ti phase. Moreover, the columnar grains between the layers were transformed into equiaxed grains and finer grains at the center of the layers. There was a significant effect of TiH on the grain refinement. The samples with Ti demonstrated superior mechanical properties. The tensile strength and elongation of the SWSs increased by 28 MPa and 4.6% in the parallel additive direction and by 37 MPa and 8.9% in the vertical direction. The addition of Ti also contributed to the even distribution of the mechanical properties in both directions.