Effects of groove on the microstructure and mechanical properties of dissimilar steel welded joints by using high-entropy filler metals

Owing to the high strength and plasticity, high-entropy alloys (HEAs) can be used as filler metals to achieve high-quality joints. However, the melting base metal in fusion welding can significantly change the chemical composition of the weld zone (WZ), which may cause the failure of high-entropy effects in the WZ. In the present study, a high-entropy filler metal of CoCrNiMnAl0.6Ti0.3Si0.1 was used to join the dissimilar metals of SMA490BW steel and 304 stainless steel. Two types of joints were obtained by whether the welding plates had a V-groove or not. The effects of workpiece groove on the microstructure, element distribution, phase structure, microhardness, and tensile strength of dissimilar joints, as well as the controllability of the high-entropy effects in WZ were explored. It was found that a 60° V-groove in the workpiece could significantly reduce the amount of Fe element in the WZ. Microstructures in the WZs were changed from columnar/equiaxed grains of the No V-groove sample to lamellar structures of the V-groove sample. The microhardness in the WZ of the latter was 33% higher than that of the former. The reason was mainly related to the phase structures in two WZs. Two types of samples had a similar notched tensile strength, which was higher than SMA490BW steel, and lower than 304 stainless steel.