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Martensitic transformations and mechanical behavior of amorphous-crystalline Ti-Ni-Cu and Ti-Hf-Ni-Cu thin ribbons
|Natalia Resnina 1, Sergey Belyaev 1, Alexander Shelyakov 2|
1. Saint-Petersburg State University, Saint-Petersburg, Russian Federation
Martensitic transformations and strain variation in amorphous-crystalline thin ribbons of Ti50Ni25Cu25, Ti40.7Hf9.5Ni44.8Cu5 and Ti40.7Hf9.5Ni39.8Cu10 alloys were investigated. The amorphous-crystalline state in the samples was produced by an interruption of the isothermal crystallization in DSC apparatus. The volume fracture of the crystalline phase (Vcr) in the samples was varied from 10 to 100 %. Transformation temperatures in amorphous-crystalline thin ribbons of Ti50Ni25Cu25 alloy depended only slightly on the crystalline volume fraction. On the contrary the strong dependence of the martensitic transformation temperatures on the volume of crystalline phase was obtained in Ti40.7Hf9.5Ni44.8Cu5 and Ti40.7Hf9.5Ni39.8Cu10 alloys. Unusual difference between the transformation intervals of the direct transition and the reverse one was found. The interval of the direct transformation was 3 oC whereas the interval of the reverse transition was 40 oC. It was shown that as the crystalline volume raised the transformation temperatures increased and the interval of the reverse phase transition reduced. Probably the main reason of the observed phenomena consisted in a various phase composition of the samples after crystallization.
The shape memory effect was observed in the amorphous-crystalline thin ribbons. Increase of the volume fracture of crystalline phase resulted in the growth of the strain recovery. The perfect shape memory effect was observed in the samples with the volume fracture of the crystalline phase exceeded 60%. It was concluded that the unelastic deformation realized in the amorphous phase as well as in the crystalline one in the case of the Vcr < 60%, otherwise the strain occurred in the crystalline grains only.
Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Natalia Resnina
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-11 13:36 Revised: 2009-06-07 00:44