Effect of grain size on amount of deformation-induced ε martensite and shape memory alloy in Fe-Mn Alloy
K. K. Jee*, J. H. Han* and W. Y. Jang**
* Division of Materials, Korea Institute of Science and Technology, Seoul 136-791, Korea
** Division of Metallurgical and Materials Engineering, Chosun University, Gwangju 501-759, Korea
In this work, a new method of measuring volume fraction of deformation-induced ε martensite for Fe-Mn alloys is proposed using endothermic heat on ε→γ transformation. The variation in the amount of ε induced by deformation with grain size is determined for an Fe-21Mn alloy, and its influence on shape memory effect is investigated.
∆H/mole on reverse transformation for the alloy is obtained by comparing ∆H and the volume fraction of martensite. The latter is calculated from dilatometric work using the specific volume difference between γ and ε.
As grain size increases, the amount of ε martensite forming on cooling increases. However, with a decrease in grain size, more ε is induced by deformation, improving shape memory effect.