Stress-temperature relationship in a Ni-Mn-Ga single crystal
|Eduard Cesari 2, Volodymyr A. Chernenko 3, J Pons 2, K Ishikawa 1|
1. Tohoku Gakuin University, Tagajo, Japan
Off-stoichiometric Ni-Mn-Ga Heusler alloys exhibit a large variety of martensitic structures as well as several accompanying phenomena, as precursor or pre-martensitic effects and inter-martensitic transformations (IMT). Both the ferromagnetic and the paramagnetic martensites tend to exhibit stress- and temperature- induced IMT. Three main martensitic phases are formed, namely 10M, 14M and 2M in the monoclinic coordinate system or, in cubic coordinates, designed as five-layer modulated tetragonal (c/a <1), seven-layer orthorhombic and non-modulated tetragonal (c/a>1), respectively.
The sequence of thermally and stress-induced inter-martensitic transformations has been studied in a Ni52.0-Mn24.4-Ga23.6 single crystal. Transmission electron microscopy through in situ cooling experiments has confirmed the thermally induced martensitic phases and their sequence. The stress-strain behavior under compression along the <110>P and <100>P crystallographic directions, at different temperatures, has also been studied for this compound and a stress-temperature phase diagram has been established.
Presentation: poster at E-MRS Fall Meeting 2005, Symposium C, by Eduard Cesari
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-19 10:37 Revised: 2009-06-07 00:44