AC/DC mixed gas tungsten arc welding of a (FeCoNi)96Al4 high-entropy alloy

Abstract

High-entropy alloys (HEA) are a unique class of engineering alloys with excellent properties, and the study of their weldability is one of the key steps in applying them in the engineering field. AC/DC mixed gas tungsten arc welding (MIX-GTAW) can achieve high-quality welding of metal components, but there are few reports on the use of MIX-GTAW for HEA welding. This study focused on the (FeCoNi)96Al4 HEA and investigated the weld formation, microstructure, and mechanical properties of the (FeCoNi)96Al4 HEA MIX-GTAW to explore the possibility of using MIX-GTAW for high-entropy alloys. The results showed that the MIX-GTAW weld seam produced fish scale patterns, and compared to those of the DC-GTAW weld seam, the surface oxidation phenomenon was improved. The microstructure of the MIX mode weld seam with 40% AC (MIX-2) is significantly improved, resulting in a smaller average grain size. The weld structure index J of MIX-2 (40% AC) is 3.27, and the maximum strength in the PF diagram decreases to 6.90. The minimum ultimate tensile strength after welding can reach 435 MPa, with an elongation after fracture of 61%, maintaining a tensile strength of 94.26% of the base material and an elongation of approximately 90%. The average hardness of the (FeCoNi)96Al4 HEA welded sample fluctuates between 167 and 180 HV, and the hardness of the center of the weld seam is higher than that of the base metal.

Keywords

• High-entropy alloy
• (FeCoNi)96Al4
• AC/DC mixed gas tungsten arc welding
• Weldability analysis
• Microstructure