The stabilization of transformation pathway in stress induced martensite
Journal Article
·
· Scripta Metallurgica et Materialia
- Czech Academy of Sciences, Prague (Czech Republic). Institute of Physics
- Mie Univ., Tsu (Japan). Faculty of Engineering
It has been recently shown that two way shape memory effect/TWSME/ in shape memory alloys/SMS/ can withstand opposite external forces (the transformation strain induced by thermal change and external stress have opposite signs) up to some level and therefore do work. The reason comes from a strong thermodynamical asymmetry among possible crystallographic martensite variants due to a preceding ``training`` procedure. For example a simple repeated stress cycling proved to be a quite efficient training technique for Cu-based SMA. One of the highly accepted views on TWSME is the idea, that the dislocation configurations formed by stress cycling of SMA are of low energy in repeatedly stress induced variants, while of high energy in other variants. The result is the stabilization of a transformation pathway and the establishment of TWSME in subsequent thermal cycling across the transformation temperature region. When the temperature is lowered below the martensite start temperature M{sub s}, those ``trained`` variants nucleate and grow preferentially even if their growth is opposed by the external bias stress up to some level. Macroscopically, the progress of thermally of stress induced MT can be characterized by the sequence of macroscopic strain states taken by the specimen during the transformation process-transformation pathway.
- OSTI ID:
- 92978
- Journal Information:
- Scripta Metallurgica et Materialia, Journal Name: Scripta Metallurgica et Materialia Journal Issue: 12 Vol. 32; ISSN SCRMEX; ISSN 0956-716X
- Country of Publication:
- United States
- Language:
- English
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