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CSME 2021/12
Volume 42 No.6
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587-594
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Diffusion Layer Growth and Compound Formation Sequence of Titanium-Carbon Steel Tri-metal Composite (Ti-Ni-steel) Sheets Fabricated by Hot-roll Diffusion Bonding
Chun-Ming Lina
aDepartment of Mechanical Engineering, Minghsin University University of Science and Technology, Hsinchu, 30401, Taiwan.
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Abstract:
The primary objective in this work was to investigate the diffusion layer growth and compound formation sequence of titanium-carbon steel tri-metal composite sheets fabricated. Those results give auseful insight into the effects of different processing temperatures on the interface evolution at the Ti/Ni interface in hot-roll diffusion-bonded Ti/Ni/ steel joints, and observations of microstructure and thermodynamic calculations revealed some interesting results. During the diffusion process, Ni3Ti and NiTi2 begin nucleation at nearly the same time; therefore, the thickness of the two layers was very similar. Finally, Ti and Ni diffuse to the interface between the NiTi2and Ni3Ti compound layers to form NiTi. As the thickness of the NiTi layer increases, part of Ni3Ti is consumed; leading to a reduction in its thickness, it can be attributed to the lower reaction Gibbs free energies and surface energy increments of Ni3Ti and NiTi2. The α + β Ti phases additionally exist as discrete needleshaped particles in the matrix of Ni3Ti phase, while βTi phases exist as discrete islands in the matrix of NiTi2 phase. The presence of Ni in the interfacial zone adjacent to the Ti substrate stabilizes β-Ti phase, leads to the formation of needle-shaped α + β-Ti phase.
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Keywords: Diffusion layer growth, Compound formation, Tri-metal composite sheets, Hot-rolling, Diffusion bonding.
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©
2021
CSME , ISSN 0257-9731
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