Optimization of the microstructure and mechanical properties of electron beam welded high-strength medium-entropy alloy (NiCoCr)94Al3Ti3

作者：Peng, Hanlin; Yi, Yaoyong^*; Fang, Weiping; Hu, Ling; Baker, Ian; Li, Liejun^*; Luo, Bingbing

来源：Intermetallics, 2022, 141: 107439.

DOI：10.1016/j.intermet.2021.107439

• Medium-entropy alloys
• Electron beam welding
• Microstructure
• Mechanical properties
• Strengthening mechanisms

The weldability and effects of subsequent heat treatment on the microstructure and mechanical properties of the medium-entropy alloy (MEA) (NiCoCr)(94)Al3Ti3 have been explored using electron beam welding (EBW). It was found that EBW joints consist of a supersaturated f.c.c. matrix with coarse, asymmetric columnar grains (17.7-24 mu m). The fraction of twins and Sigma 3(n) CSL boundaries in weld joints was only 10% of that in the base metal, a value which increased to 30% after aging at 800 C. The aging also led to improvements in the hardness, tensile strength, and work hardening rate, a result of the precipitation of a high volume fraction (0.29-0.33) of ultrafine (15-17.4 nm dia.) coherent spherical L1(2)-structured particles. The contributions of the L1(2) nano particles and Hall-Petch strengthening to the yield strength were estimated to be 537-573 MPa and 105-123 MPa, respectively. The MEA shows excellent weldability and, after aging, good strength (YS-1098 MPa, UTS similar to 1368 MPa) and elongation to failure similar to 11%) by ductile fracture.