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Dissimilar fusion welding of NiTi shape memory alloy and AlCoCrFeNi2.1 eutectic high entropy alloy using multi-interlayer strategy
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Resumo(s)
Dissimilar fusion welding between NiTi shape memory alloy and AlCoCrFeNi2.1, eutectic high entropy alloy was achieved using a combination of Nb and Cu interlayers. Both base metals exhibit unique properties that complement each other making them attractive for integration in smart systems. However, direct joining of these materials is not feasible due to the formation of brittle intermetallic compounds that compromise the joint integrity. Thus, to avoid this metallurgical issue dissolution of the Nb and Cu interlayers promoted elemental intermixing and altered solidification pathways, leading to the formation and intensification of topologically close-packed phases. Phase evolution was assessed through thermodynamic CALPHAD simulations and validated using synchrotron X-ray diffraction, while further microstructural characterization employed backscattered electron imaging and energy dispersive spectroscopy. The weld exhibited pronounced spatial heterogeneity, with a peak hardness of 856 HV0.3 near the NiTi-side interfacial region, consistent with enrichment of TCP phases and Ti-rich intermetallics. Tensile testing showed fracture at an ultimate tensile strength of 372 MPa and a fracture strain of 1.11%, with crack initiation in the hardened interfacial region followed by mixed-mode fracture toward the fusion zone. Although tensile ductility remains limited, the multi-interlayer strategy enabled defect-free joint formation and confined embrittlement to a narrow region compared with direct joining.
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Publisher Copyright: © 2026 The Author(s)
Palavras-chave
AlCoCrFeNi eutectic high entropy alloy Dissimilar fusion welding Mechanical characterization Multi-interlayer diffusion barrier NiTi shape memory alloy Synchrotron X-ray diffraction Thermodynamic simulation General Materials Science Condensed Matter Physics Mechanics of Materials Mechanical Engineering