Deformation of hierarchically twinned martensite
| Title | Deformation of hierarchically twinned martensite |
| Publication Type | Journal Article |
| Year of Publication | 2010 |
| Authors | Mullner P, King AH |
| Journal Title | Acta Materialia |
| Volume | 58 |
| Pages | 5242-5261 |
| Date Published | 9 |
| ISBN Number | 1359-6454 |
| Accession Number | ISI:000281318900003 |
| Keywords | crystal, defects, disclination models, Disclinations, domain pattern, INTERFACES, JUNCTIONS, Martensitic phase transformation, microstructure, mild-steel, PHASE-TRANSFORMATIONS, shape-memory alloys, shape-memory alloys (sma), twinning, yba2cu3o7-delta |
| Abstract | Shape-memory alloys deform via the reorganization of a hierarchically twinned microstructure. Twin boundaries themselves present obstacles for twin boundary motion. In spite of a high density of obstacles, twinning stresses of Ni-Mn-Ga Heusler alloys are very low. Neither atomistic nor dislocation-based models account for such low yield stresses. Twinning mechanisms are studied here on a mesoscopic length scale making use of the disclination theory. In a first approach, a strictly periodic twin pattern containing periodic disclination walls with optimally screened stress fields is considered. Strict periodicity implies that the twin microstructure reorganizes homogeneously. In a second approach, a discontinuity of the fraction of secondary twins is introduced and modeled as a disclination dipole. The stress required for nucleation of this discontinuity is larger than the stress required for homogeneous reorganization. However, once the dipole is formed, it can move under a much smaller stress in agreement with experimental findings. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. |
| URL | <Go to ISI>://000281318900003 |
| DOI | 10.1016/J.Actamat.2010.05.048 |
