Martensitic transformation behaviors of Ti-rich Ti–Ni alloy fibers fabricated by melt overflow

• Ti2Ni precipitates were distributed in the grains for the of Ti50.5Ni49.5 alloy.
• Ti2Ni was formed at grain boundaries for the Ti51.5Ni48.5 alloy.
• Addition of 0.5% Ti in Ti50Ni50 alloy increased the transformation temperatures.

Ti50Ni50, Ti50.5Ni49.5, Ti51Ni49 and Ti51.5Ni48.5 fibers were fabricated by melt overflow process. The rapid solidification can increase the solubility above the equilibrium solubility. The effects of the rapid solidification of Ti-rich Ti–Ni alloys on the microstructure, transformation temperatures and shape memory characteristics are investigated. The addition of 0.5 at.% Ti in Ti50Ni50 alloy greatly increases the transformation temperature. However, the transformation temperatures decrease again for Ti content exceeding 51 at.%. Results of thermal cycling tests under various constant stress levels reveal that the recoverable elongation associated with B2–B19 martensitic transformation of Ti50.5Ni49.5 fibers is two times larger than that of Ti51.5Ni48.5 alloy fiber.

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