Two types of the first cycle effects in copper based shape memory alloys
The effects of thermo mechanical treatments on transformation temperatures and hysteresis are important for many shape memory applications. Depending on the field of application either a large or small hysteresis is required. A high hysteresis for the first cycle is especially important for one way applications, when the material has to be stored in the transformable martensitic condition. For this reason the material is deformed slightly in the martensitic state (T{sub MF}<M{sub f}). The A{sub s} and A{sub f} temperatures are increased by this treatment for the first transformation cycle. For the following cycles these temperatures nearly regain the value of the undeformed state. It is known from several investigations that the martensite transformation temperatures depend on the thermo-mechanical history of the alloy. Treppman et al., Spielfeld et al. and also Zhang et al. found that the defects formed in martensite domain boundaries are able to induce a shift of austenite temperatures to significantly higher values and thus increase the transformation hysteresis of the first cycle. In this work it will be shown that a different first cycle effect occurs after ausforming of the Copper based shape memory alloy. For the first cycle the A{sub s} temperature is lowered. For the following DSC cycles it is increased nearly to its original value after betatising.
- Research Organization:
- Ruhr Univ. Bochum (DE)
- OSTI ID:
- 20023097
- Journal Information:
- Scripta Materialia, Vol. 40, Issue 12; Other Information: PBD: 21 May 1999; ISSN 1359-6462
- Country of Publication:
- United States
- Language:
- English
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