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MM: Fachverband Metall- und Materialphysik

MM 63: Computational Materials Modelling - Phase Stability IV

MM 63.6: Talk

Thursday, March 14, 2013, 18:30–18:45, H24

Ion-Irradiation-Assisted Phase Selection in Single Crystalline Fe7Pd3 Ferromagnetic Shape Memory Alloy Thin Films: From fcc to bcc along the Nishiyama-Wassermann Path — •Ariyan Arabi-Hashemi¹ and Stefan G. Mayr^1,2,3 — ¹Leibniz-Institut für Oberflächenmodifizierung e.V., Leipzig, Germany — ²Translationszentrum für Regenerative Medizin, Universität Leipzig, Germany — ³Fakultät für Physik und Geowissenschaften, Universität Leipzig, Germany

Fe7Pd3 exhibits four different metastable phases: the austenite fcc phase and three martensite phases (fct, bct, and bcc). Our work aims at exploring the influence of generalized internal stresses due to (i) point defects and (ii) deviations from equilibrium short-range order. While the former are stresses in a strict mechanical sense, the latter are the conjugate variable of the short-range order parameter. In a given sample, manipulation of both, (i) and (ii) can conveniently be achieved by means of irradiation with energetic ions. 500 nm thick single crystalline Fe7Pd3 films were deposited at 850°C on MgO (001) single crystalline substrates. The unirradiated samples exhibit prevalently the austenite fcc phase. These thin films were ion-irradiated with 1.8 MeV Kr+ -ions. Fluency dependant T2T-measurements show that ion-irradiation-assisted phase selection along the whole transformation path ranging from fcc->bcc is possible. Fluency dependant pole figure measurements describe the fcc->fct and the transformation into the bcc phase in detail. An orientation relationship according to Nishiyama-Wassermann for the fcc->bcc transformation is observed.