In this study, laser-directed energy deposition was applied to build a Ti-rich ternary Ti-Ni-Cu shape-memory alloy onto a TiNi shape-memory alloy substrate to realize the joining of the multifunctional bi-metallic shape-memory alloy structure. The cost-effective Ti, Ni, and Cu elemental powder blend was used for raw materials. Various material characterization approaches were applied to reveal different material properties in two sections. The as-fabricated Ti-Ni-Cu alloy microstructure has the TiNi phase as the matrix with Ti2Ni secondary precipitates. The hardness shows no high values indicating that the major phase is not hard intermetallics. A bonding strength of 569.1 MPa was obtained by tensile testing, and digital image correlation reveals the different tensile responses of the two sections. Differential scanning calorimetry was used to measure the phase-transformation temperatures. The austenite finishing temperature of higher than 80°C was measured for the Ti-Ni-Cu alloy section. For the TiNi substrate, the austenite finishing temperature was tested to be near 47°C at the bottom and around 22°C at the upper substrate region, which is due to the repeated laser scanning that acts as annealing on the substrate. Finally, the multiple shape-memory effect of two shape-memory alloy sides was tested and identified.
Y. Chen et al., "TiNi-Based Bi-Metallic Shape-Memory Alloy by Laser-Directed Energy Deposition," Materials, vol. 15, no. 11, article no. 3945, MDPI, Jun 2022.
The definitive version is available at https://doi.org/10.3390/ma15113945
Materials Science and Engineering
Mechanical and Aerospace Engineering
Keywords and Phrases
Additive Manufacturing; Directed Energy Deposition; Elemental Powders; Joining of Metals; Shape-Memory Alloys
International Standard Serial Number (ISSN)
Article - Journal
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Creative Commons Licensing
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01 Jun 2022
This research was partially funded by the U.S. Department of Energy STTR Contract DE-SC0018879, the National Science Foundation Grants CMMI 1625736, and the Material Research Center at Missouri S&T.