Effect of Wire Feed Speed on Microstructure and Mechanical Properties of 205C Aluminum Alloy in CMT+P‐Based Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) of precipitation‐strengthened Al–Cu alloys is highly sensitive to heat input, which often causes porosity and microstructural coarsening. In this work, double‐pass thin‐walled 205C Al alloy deposits were fabricated by Cold Metal Transfer plus Pulse (CMT + P) under controlled deposition conditions, with wire feed speed (WFS) varied from 6.6 to 7.2 m·min −1 as the primary control variable. All deposits consisted mainly of fine equiaxed grains. Increasing WFS refined the grains by about 18% and increased the fraction of high‐angle grain boundaries, but the response was nonmonotonic. At 7.0 m·min −1 , the deposit showed the lowest porosity, the most continuous grain‐boundary network, the narrowest kernel average misorientation distribution, and the finest, most uniformly dispersed Cu‐rich θ‐family platelets. Mechanical testing revealed pronounced anisotropy: transverse elongation reached 12.75% at 7.2 m·min −1 , whereas longitudinal elongation peaked at 11.0% at 6.8 m·min −1 . At 7.0 m·min −1 , transverse tensile strength reached 256.4 MPa, elastic modulus showed minimal scatter, and microhardness was most homogeneous across height and between adjacent passes. Overall, 7.0 m·min −1 provides the best balance among densification, microstructural homogeneity, and strength–ductility performance under the present controlled CMT + P conditions.