Abstract
The addition of Nb can form a eutectic phase with a NiTi matrix in a NiTi-based shape memory alloy, improving the transition hysteresis of the NiTi alloy. A Ni44Ti44Nb12 ingot was prepared using the vacuum induction melting technique. Under compression deformation, the yield strength of the NiTi–Nb alloy is about 1000 MPa, the maximum compressive strength and strain can reach 3155 MPa and 43%, respectively. Ni44Ti44Nb12 exhibited a superelastic recovery similar to that of the as-cast NiTi50. Meanwhile, the loading–unloading cycle compression shows that the superelastic recovery strain reached a maximum value (2.32%) when the total strain was about 15%, and the superelasticity tends to rise first and then decrease as the strain increases.
Highlights
NiTi alloys represent an important type of shape memory alloys (SMA), with unique superelasticity and a distinct shape memory effect
As in typical NiTi-based ternary alloys, Nb plays an important role in NiTi–Nb alloys, because the addition of Nb increases the transition hysteresis of NiTi alloys [10,11]
The phase diagram shows that the eutectic temperature is far lower than the melting point of Ni, Ti, and Nb, and the reaction temperature can reach 1180 ◦ C to ensure the formation of the eutectic phase [18,19]
Summary
NiTi alloys represent an important type of shape memory alloys (SMA), with unique superelasticity and a distinct shape memory effect They have attracted considerable attention in aerospace engineering and the industrial and biomedical fields [1,2,3,4,5]. Compared with other SMAs, such as iron-based and copper-based alloys, NiTi-based SMA have high strength and plasticity, good corrosion resistance, and excellent biocompatibility. They have a great potential for biomedical applications [6,7,8,9]. Cyclic loading–unloading compression was carried out on the NiTi–Nb sample, whose dimension was Φ4 × 6 mm. All the samples were compressed at a loading rate of 0.1 mm/min at room temperature
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