2108 Superelastic Behavior of AuTi-18Co Alloys

Hosoda, Hideki; Tsugane, Yasuhito; Inamura, Tomonari; Wakashima, Kenji; Miyazaki, Shuichi

doi:10.1299/jsmemecjo.2007.1.0_153

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“…Actually, the critical stress for slip in 2Nb is evaluated to be around 150 MPa while that in AuTi-18 mol%Co superelastic alloy with similar grain size is about 50 MPa. 14) However, the details of strengthening by Nb addition will be studied more precisely.…”

Section: Shape Memory and Superelastic Propertiesmentioning

confidence: 99%

Effect of Nb Addition on Martensitic Transformation Behavior of AuTi-15Co Based Biomedical Shape Memory Alloys

et al. 2015

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The effect of quaternary addition of Nb being from 0 to 2 mol% on the phase constitution, phase transformation behavior and shape memory behavior of Au-50 mol%Ti-15 mol%Co (AuTiCo) alloys is studied. X-ray diffraction analysis shows that, with increasing Nb concentration, the primary phase appeared at room temperature changes from B19 orthorhombic martensite phase to B2 cubic parent phase, and that all the lattice parameters are not largely changed by Nb addition. The maximum transformation strain evaluated in 2 mol%Nb-added AuTiCo is 7.4%. Differential scanning calorimetry revealed that the reverse martensitic transformation finish temperature (A f ) decreases from 414 K in Nb-free AuTiCo to 303 K by 2 mol%Nb addition. The ratio of A f change by Nb addition is evaluated to be ¹55 K/mol%Nb, that is comparably larger than ¹31 K/mol%Nb in NiTi. These results indicate that Nb addition is effective to stabilize B2 parent phase. AuTiCo alloy containing less than 2 mol%Nb exhibits shape memory effect with 90% shape recovery ratio. Besides, AuTiCo containing 2 mol%Nb exhibits 2.8% superelastic shape recovery at room temperature as well as 7.4% maximum transformation strain. Therefore, Nb addition to AuTiCo is effective to decrease the martensitic transformation temperature and to improve superelasticity, although the transformation temperature hysteresis increases by Nb addition, similar to Nb-added NiTi.

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Section: Shape Memory and Superelastic Propertiesmentioning

confidence: 99%