| Summary: | This study presents a novel approach for developing hard pseudoelastic TiNiCu ternary shape memory alloy (SMA) using laser-directed energy deposition (LDED). We harness the thermocapillary convection to achieve effective material transport by depositing a Cu-Ni powder premix while extracting Ti from the substrate. This approach overcomes the challenges of powder oxidation, agglomeration, handling, and powder recycling associated with conventional additive manufacturing of Ti-based SMAs. The alloy composition is driven by thermocapillary flow, with a Marangoni number significantly higher than the Grashof number. Microstructural analysis reveals the presence of the NiTi-B2 austenitic phase, which is responsible for remarkable pseudoelasticity and reduced hysteresis, with recovery ratios exceeding 90%. Enhanced microhardness (500 HV0.2) is attributed to the formation of hard intermetallic phases. The pseudoelasticity and microhardness values are among the highest reported for any SMA developed via an additive manufacturing route. This ternary SMA has huge potential in biomedical, aerospace, and sensing applications.
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