Large-Area AA6061 Alloy Sheets Prepared via Multi-pass Particles-Based Additive Friction Stir Deposition

In this study, large-area fine-grained AA6061 alloy sheets were fabricated using additive friction stir deposition (AFSD) and jet-cooling-assisted AFSD (JAFSD) with a rotational speed of 400 r/min and a forward speed of 100 mm/min. Results demonstrated that both specimens consisted of two typical zones: central zone and interfacial zone. In AFSD specimens, the grain size distribution in the central and interfacial zones exhibited uniformity (6.9 to 8.5 μm), albeit with differences in precipitate phase distribution. The central zone consisted primarily of a small number of coarsened Mg₂Si phases, minor β′ phases, and abundant ultrafine Mg₂Si phases, whereas the ultrafine Mg₂Si phases dissolved in the interfacial zone. Comparably, the JAFSD specimens exhibited finer and more uniform grain size throughout the central and interfacial zones (3.7 to 4.9 μm), while maintaining similar precipitate phase characterized by coarsened Mg₂Si phases, β′ phases, and predominant ultrafine Mg₂Si phases. Notably, the AFSD specimens showed lower microhardness and strength in the interfacial zone (50 to 52 HV, 130 MPa) than the central zone (52 to 62 HV, 167 MPa). In contrast, JAFSD specimens maintained consistent properties across both zones (Central: 50 to 58 HV, 170 MPa; Interfacial: 50 to 58 HV, 161 MPa), demonstrating JAFSD could fabricate the large-area AA6061 alloy sheets with uniform microstructures and strength.

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