A novel pathway to weld forming control and microstructure improvement of duplex stainless steel via alternating magnetic field

In this paper, a novel arc oscillation welding method, namely, the arc oscillation along the welding direction with the aid of alternating magnetic field, is adopted to weld thin-walled 2205 duplex stainless steel in autogenous mode. The oscillating arc can route some effects on the weld forming as well as the microstructure evolution of weld zone, which in turn affects the weld performance. The results show that such arc oscillation can alleviate the surface root sagging of the weld during the conventional GTAW process, and the improvement effect becomes more pronounced with the increase of excitation frequency. Simultaneously, the heat affected zone of the weld with magnetic field at a higher frequency becomes narrower. Based on the reheating effect of arc oscillation on the molten pool, gamma/alpha (austenite/ferrite) phase ratio in the weld zone are regulated. At an excitation frequency of 10 Hz, the weld with gamma/alpha ratio nearly 1:1 is obtained. Meanwhile, arc oscillation can manipulate the texture characteristics of weld microstructure, which follows that the higher the excitation frequency, the lower the texture density. Eventually, the strength and plasticity of the weld are improved synergistically at a higher magnetic field frequency in this work.