UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2019 Meeting


Section: Solid State Physics and Materials Science


Title:
Effect of Mn substitution on the structural, magnetic and magnetostrictive properties of Fe-Pd ferromagnetic shape memory alloy prepared as ribbons


Authors:
Mihaela SOFRONIE (1), F. TOLEA (1), M. ENCULESCU (1), A.D. CRISAN (1)


Affiliation:
1) National Institute of Materials Physics, POB MG-7, 77125 Magurele, Romania


E-mail
mihsof@infim.ro


Keywords:
ferromagnetic shape memory alloys, martensitic transformation, magnetostriction, magnetic field-induced strains


Abstract:
Ferromagnetic shape memory alloys (FSMA) have attained strong interest over the last years because of the large strains which can be obtained by the application of an external magnetic field. The Fe-Pd based FSMA are promising materials, due to the better mechanical properties and high Curie temperature (~760 K). The shape memory effect in disordered Fe–Pd (30 at.% Pd) is associated with an f.c.c - f.c.t. thermoelastic martensitic transformation (MT). A non-thermoelastic and irreversible f.c.t.-b.c.t. MT may be evidenced on further cooling [1]. Rapid solidification, by using a melt-spinning technique, is an effective processing route to obtain ribbons with a non-equilibrium structure, in which the high temperature f.c.c. structure can be frozen as single phase [2-3]. In order to stabilize the f.c.t. martensite, i.e. to avoid the formation of the undesirable b.c.t. martensite and to manipulate the transformation temperatures, the Mn addition, as a third alloying element in Fe-Pd system was studied [4]. Prepared as ribbons by rapid quenched technique, these alloys are suitable for sensors designs. The influence of Mn substitution, rapid solidification technique and heat treatments on the martensitic transformation, magnetic and magnetostrictive properties on Fe70-xPd30Mnx (x=1,3) ribbons were investigated. The thermal treatments induce significant changes in the microstructure and magneto-crystalline anisotropy of the martensitic phase. The segregation and growth of precipitates, on account of the main transformable phase is considered to contribute essentially to the suddenly increase of the MT temperature (via the depletion of the main phase in Mn and Pd content) and the different magnetic behavior. The magnetostriction measurements indicate the magnetic moments rotation as the predominant mechanism in martensitic state, for as prepared ribbons; the thermal treatments may induce an increased magneto-crystalline anisotropy and the magnetic field-induced strains are enhanced due to the martensitic variants reorientation mechanism. The competition between the magnetization orientation and twin boundary motion within martensitic variants under magnetic field, evidenced by the magnetic-strain curves is discussed and correlated with the magnetic data.


References:

[1] R.D. James, M. Wuttig, Magnetostriction of martensite, Phil. Mag. A 77, (1998), 1273-1299.

[2] D. Vokoun, C. T. Hu, Thermomechanical and magnetic properties of the as-spun Fe–Pd SMA ribbons, J. Alloys Compd. 346 (2002) 147-153

[3] M. Sofronie, F. Tolea, V. Kuncser, M. Valeanu, G. Filoti Magneto-structural Properties and Magnetic Behaviour of Fe-Pd Ribbons”, IEEE Trans. on Mag. 51, (2015), 2500404.

[4] V Sánchez, V. Recarte, J.I. Pérez-Landazábal, M.A. González, J.A. Rodríquez-Valamazán, Acta Materialia, Effect of Mn addition on the structural and magnetic properties of Fe–Pd ferromagnetic shape memory alloys 57 (2009) 4224-4232;



Acknowledgement:
This work was supported by Grant of Romanian Ministry of Research and Innovation, CCCDI-UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0062/contract no.58/component project no.2, within PNCDI III.