Improvement of forming quality, microstructure, and mechanical performance of high-efficient wire-arc additive manufactured Al-5%Mg alloy assisted by oscillating alternating magnetic field

Producing Al-5%Mg alloy with ultra-fine forming quality, low defect rates, and desirable mechanical properties under high-efficiency deposition conditions (without waiting time between deposition layers) using cold metal transfer wire-arc additive manufacturing (CMT-WAAM) technology remains a considerable challenge. In this study, Al-5%Mg thin-walled components were successfully fabricated using a self-designed oscillating alternating magnetic field (SOAM) assisted high-efficiency CMT-WAAM process. Results show that compared with the CMT-WAAM process without SOAM, the application of SOAM induced the arc to oscillate about 60 degrees in the forward direction, effectively mitigating the backward flow of molten metal, enhancing the convection state within the molten pool, suppressing hump formation during the high-efficiency deposition process, and significantly improving the geometric accuracy of thin-walled parts. The periodic oscillation and stirring effect of SOAM on the molten metal reduced the average grain size of the deposition layer from 75.54 mu m to 63.57 mu m, with the proportion of grains smaller than 50 mu m increasing from 31.2 % to 39.4 %. The defect rate, as determined by micro-CT scanning, was reduced from 0.993 % to 0.537 %. The average microhardness of the deposited specimen increased from 69.9 HV0.2 to 81.5 HV0.2, reflecting a 16.7 % improvement. Additionally, the longitudinal tensile strength increased from 248 MPa to 267 MPa, while the transverse tensile strength rose from 268 MPa to 273 MPa. Yield strength and elongation at break also demonstrated improvements, nearing isotropy. This investigation provides an effective strategy and theoretical framework for achieving high forming quality and superior mechanical properties in aluminum alloy components produced through high-efficiency WAAM.