On the multiplication of dislocations during martensitic transformations in NiTi shape memory alloys

0354828 - ÚFM 2011 RIV GB eng J - Článek v odborném periodiku
Simon, T. - Kröger, A. - Somsen, Ch. - Dlouhý, Antonín - Eggeler, G.
On the multiplication of dislocations during martensitic transformations in NiTi shape memory alloys.
Acta Materialia. Roč. 58, č. 5 (2010), s. 1850-1860. ISSN 1359-6454. E-ISSN 1873-2453
Grant CEP: GA ČR GA106/09/1913
Výzkumný záměr: CEZ:AV0Z20410507
Klíčová slova: NiTi * Martensitic transformations * Dislocation multiplication mechanism * Martensite variants * Dislocations
Kód oboru RIV: BM - Fyzika pevných látek a magnetismus
Impakt faktor: 3.781, rok: 2010

In situ and post-mortem diffraction contrast transmission electron microscopy (TEM) was used to study the multiplication of dislocations during a thermal martensitic forward and reverse transformation in a NiTi shape memory alloy single crystal. An analysis of the elongated dislocation loops which formed during the transformation was performed. It is proposed that the stress field of an approaching martensite needle activates an in-grown dislocation segment and generates characteristic narrow and elongated dislocation loops which expand on {1 1 0}B2 planes parallel to {0 0 1}B190 compound twin planes. The findings are compared with TEM results reported in the literature for NiTi and other shape memory alloys. It is suggested that the type of dislocation multiplication mechanism documented in the present study is generic and that it can account for the increase in dislocation densities during thermal and stress-induced martensitic transformations in other shape memory alloys.
Trvalý link: http://hdl.handle.net/11104/0193743