ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Magnetic shape-memory alloys owe their exceptional properties primarily to theaccompanying effects of a martensitic phase transformation. The twinning disconnection aselementary carrier of magnetic-field-induced deformation is the starting point of the present study.A disconnection is a line defect similar to a dislocation but located at an interface and exhibiting astep character besides a dislocation character. The mutual interaction of disconnections is fullytractable by the theory of dislocations. Due to the martensitic transformation, a hierarchical twinmicrostructure evolves, details of which are controlled through disconnection-disconnectioninteraction. Depending on the mutual orientation of twin boundaries on different hierarchical levels,twinning disconnections are incorporated in higher hierarchical twin boundaries formingdisclination walls, or they stand off individually from those interfaces. Disconnections which standoff from interfaces contribute to magnetoelasticity, i.e. recoverable magnetic-field-induceddeformation. Disconnections in disclination walls contribute to magnetoplasticity, i.e. permanentmagnetic-field-induced deformation, if the twin thickness is large. In self-accommodated martensitewith very thin twins, resulting from a martensitic transformation without training, the deformation isfully magnetoelastic and small. In single-domain crystals, resulting from effective thermo-magnetomechanicaltraining, the deformation is fully magnetoplastic and large. Between these limitingcases, there is a continuous spectrum where, as a rule, the fraction of magnetoplastic strain and thetotal strain increase with increasing effectiveness of training
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.583.43.pdf
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