| Titre : | Highly mobile twinned interface in 10 M modulated Ni–Mn–Ga martensite : Analysis beyond the tetragonal approximation of lattice (2012) |
| Auteurs : | L. Straka, Auteur ; O. Heczko, Auteur ; H. Seiner, Auteur |
| Type de document : | Article : texte imprimé |
| Dans : | Acta materialia (Vol. 59 N° 20, Décembre 2011) |
| Article en page(s) : | pp. 7450–7463 |
| Note générale : | Métallurgie |
| Langues : | Anglais |
| Tags : | Microstructure Twinning X-ray diffraction Heusler phases Magnetic shape memory |
| Résumé : | The huge strains that Ni–Mn–Ga magnetic shape memory alloys can achieve are usually described in a tetragonal unit cell approximation of a five-layered modulated (10 M) crystal structure. Here we analyze the impact of a slight orthorhombic and monoclinic distortion of the 10 M structure in Ni50.2Mn28.3Ga21.5at.% single crystal. Combining dedicated experiments to probe the microstructure, structure and mechanical properties with calculation using elastic continuum theory, we prove the existence of fine a/b-laminates within modulation macrotwins of the order of 100 micrometers in size. This complex twin microstructure containing a Type II macrotwin interface is associated with an extraordinarily low twinning stress of between 0.05 and 0.3 MPa, while Type I twins exhibit twinning stress of about 1 MPa. The findings provide important guidelines for designing the martensitic microstructure for more efficient actuators. |
| ISSN : | 1359-6454 |
| En ligne : | http://www.sciencedirect.com/science/article/pii/S1359645411006574 |
