Crystallography-driven deciphering of microstructural gradients in wire-arc additively manufactured components and promotion of microstructural homogeneity

This study systematically investigates the microstructure of wire-arc additively manufactured heat-resistant aluminium alloys through crystallographic parameter analysis, focusing on gradient evolution mechanisms and their implications. The distinct Ni incorporation methods yield different microstructure: The ACN specimens characteristic gradients transitioning from coarse-grained (CG) to fine-grained (FG) regions, evolving from high-dislocation-density columnar grains (exhibiting elevated strain and predominant low-angle boundaries) to low-dislocation-density equiaxed grains (dominated by high-angle boundaries and enhanced Schmid factors). Conversely, ACNP specimens achieve homogeneous equiaxed microstructures through rapid dissolution of interlayer Ni powder that forms microscale liquid pools. Complementary to the crystallographic analysis, the ACNP specimens exhibiting uniformly dispersed micro-pores, Weakened the stress concentration effect, further homogenising plastic flow at both micro- and meso-scales. The crystallographic gradient analysis establishes direct correlations between thermal history, dislocation substructures, and boundary evolution, revealing how powder-induced nucleation fundamentally transforms solidification dynamics by replacing directional growth with isotropic grain development – a novel insights for next-generation WAAM-processed heat-resistant alloys requiring balanced thermomechanical performance.