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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Superelastic effect in polycrystalline ferrous alloys.
1Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan. omori@material.tohoku.ac.jp
Science (New York, N.Y.)
|July 2, 2011
Summary
Superelastic alloys can recover their shape after large deformation. Iron-manganese-aluminum-nickel shape memory alloys exhibit minimal temperature-dependent superelastic stress due to magnetic effects, enabling wider applications.
Area of Science:
- Materials Science
- Metallurgy
- Solid State Physics
Background:
- Superelastic alloys deform largely and recover shape upon stress removal.
- High temperature dependence of superelastic stress limits practical applications.
- Iron-manganese-aluminum-nickel (Fe-Mn-Al-Ni) alloys are investigated for shape memory properties.
Purpose of the Study:
- To investigate the temperature dependence of superelastic stress in Fe-Mn-Al-Ni shape memory alloys.
- To understand the role of magnetic contributions in the Gibbs energy of transformation.
- To assess the potential for wide-temperature range applications.
Main Methods:
- Experimental characterization of superelastic behavior in polycrystalline Fe-Mn-Al-Ni alloys.
- Thermodynamic analysis considering magnetic contributions to Gibbs energy.
- Measurement of superelastic stress variation over a wide temperature range.
Main Results:
- Fe-Mn-Al-Ni alloys exhibit a small temperature dependence of superelastic stress.
- This is attributed to a small transformation entropy change influenced by magnetic effects.
- One alloy composition showed a stress variation of only 0.53 MPa/°C from -196 to 240°C.
Conclusions:
- The magnetic contribution to Gibbs energy significantly reduces the temperature dependence of superelastic stress in Fe-Mn-Al-Ni alloys.
- These alloys demonstrate potential for applications requiring stable superelastic performance across a broad temperature spectrum.
- The findings pave the way for advanced shape memory alloy designs with enhanced thermal stability.
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