Revealing the microstructural evolution and mechanical properties of the AlCoCrFeNi2.1/316L dissimilar spot welded joints

With its high strength, resistance to corrosion, resistance to wear, and stability at high temperatures, AlCoCrFeNi 2.1 exhibits a potential application value in the nuclear power industry. However, investigation on the dissimilar spot welding of AlCoCrFeNi 2.1 and 316L stainless steel is pretty urgent, due to its latent application value in the fabrication of fuel cladding and end plugs. In this work, the AlCoCrFeNi 2.1 /316L dissimilar spot-welded joints were obtained under various currents and electrode forces. Results show that the nugget shows distinctive columnar grains, with a typical dendritic and interdendritic microstructure, which is confirmed as austenite by the typical Schaeffler diagram. Welding cracks within the nugget were attributed to larger shrinkage distortion in 316L stainless steel and vaporization of Ni, confirmed by the spot welding simulation. Electron backscattered diffraction analysis suggested that the grain size within the nugget progressively grows from 16.29 μm to 18.46 μm, as the welding current increases from 6.66 kA to 9.75 kA, whereas it notably refines to 26.12 μm from 33.12 μm, as the electrode pressure rises from 1.5 kN to 2.5 kN. The overall hardness distribution demonstrated that the hardness in the nugget is comparable to 316L base metal, regardless of electrode pressure or current. Even accompanied by a shrinkage voids within the nugget, the peak load of the spot-welded joints still rises as the current increases, with the range of the peak load from ∼11.61 kN to ∼18.70 kN. The corresponding two fracture modes were thereupon discussed. This study reveals the microstructure formation and mechanical properties of AlCoCrFeNi 2.1 /316L dissimilar spot welded joints, which provides a foundation for the HEA/stainless steel spot welding application in the nuclear power reactor.