Abstract

The Unified Additive-Deformation Manufacturing Process (UAMFSP) integrates MIG-based Wire Arc Additive Manufacturing (WAAM) with interlayer Friction Stir Processing (FSP) on a single CNC platform, applying severe plastic deformation to each deposited layer. The novelty of this work is the first controlled comparison, to the authors’ knowledge, of the spatial position of forced-air cooling applied concurrently with the FSP traverse in such an integrated platform: cooling was directed at the top bead surface (TC), at the bottom substrate (BC), or at both surfaces simultaneously (DC), with a MIG-only wall serving as the baseline. Single-layer, four-bead ER4043 aluminum walls were deposited on AA6061 substrates, and optical micrographs from three within-bead locations per condition were quantified with ImageJ, yielding 2038 to 2723 grains per condition. A lumped-parameter thermal model calibrated to infrared thermography ranked the comparative cooling rates as NC < TC < BC < DC. The principal finding is grain homogenization: every FSP condition reduced the grain area scatter by 55 to 71 percent relative to MIG-only, eliminating the coarse-grain tail of the as-deposited distribution regardless of cooling position. Mean equivalent diameters of all four conditions lie within 0.5 µm of one another, at the resolution limit of the optical measurement, so the mean-size ordering (DC finest, 2.76 µm) is reported as a ranking rather than as net refinement. Vickers microhardness on the MIG-only and uncooled FSP walls revealed a 27 HV within-wall gradient (86 ± 7 HV at the stir-zone center versus 59 ± 2 HV at the bead edge), which motivates bilateral cooling for thermal-field homogenization. Because the design is single-replicate, between-condition differences are presented as hypotheses for replicate study with EBSD and spatially resolved hardness mapping.

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