Energy evaluation for twinning plane movement under magnetic field in ferromagnetic shape memory alloys

Issue title: E-MRS Fall Meeting 2005

Article type: Research Article

Authors: Kakeshita, Tomoyuki^a | Fukuda, Takashi^a

Affiliations: [a] Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, Osaka, Japan

Abstract: We have made an energy evaluation for the rearrangement of martensite variants (RMV) under a magnetic field using four types of ferromagnetic shape memory alloys: an Fe-31.2at. %Pd with so-called fct martensite, a Ni_2MnGa with the 10 M martensite, a Ni_{2.02}Mn_{1.09}Ga_{0.89} with the 14 M one and a Ni_{2.14}Mn_{0.92}Ga_{0.94} with the 2 M one. The RMV by a magnetic field occurs at any temperature for the Fe-31.2Pd and the 10 M martensite. However, it occurs in a limited temperature range for the 14 M martensite and does not occur at any temperature for the 2 M martensite. The reason of such different behavior is quantitatively explained by evaluating two shear stresses: the magnetic shear stress acting across a twinning plane τ_{mag}, and the stress required for the twinning plane movement τ_{req}. That is, by comparing the value of τ_{mag} and τ_{ req} thus evaluated, we have confirmed that the following condition is universal regardless of temperature, field direction and structure of the martensite phase: the value of τ_{mag} is larger than τ_{req} when the RMV occurs by magnetic field and vice versa.

DOI: 10.3233/JAE-2006-715

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 45-50, 2006