Mössbauer and Calorimetry Study of Fe-Mn-Si Shape Memory Alloys

MARTÍNEZ J.; COTES S. M.; DESIMONI J

Rio de Janeiro Brasil

Conferencia; 10th Latin American Conference on Applications of the Mössbauer Effect (LACAME '2006); 2006

CBPF-Brasil

The Fe-Mn-Si system hold a large attention of researchers in the last 25 years because of the presence of the so-called shape memory effect along with good thermomechanical properties, and a relative cheap preparation cost on industrial scale. These characteristics make this kind of alloys attractive for practical uses. Anyhow, it was experimentally observed that some properties (i.e. resistance to corrosion) can be improved by a small addition of one or more components, like Cr and Ni. The shape memory effect in Fe-Mn-Si alloys is governed by the martensitic transformation between g (FCC) and e (HCP) phases, which are metaestable phases of the system. A quenching from about 1000 ºC is needed in order to retain these phases around room temperature. To produce a thermodynamic description of the phases in multicomponent systems capable of predicting alloys with better properties, complete information about physical properties of g and e are needed even for the basic system Fe-Mn-Si. We are interested in the acquisition of new experimental data on g and e phases in the Fe-Mn-Si system which can be useful to assess the most recent thermodynamic description of both phases, g and e. We use a combination of Mössbauer spectroscopy and differential scanning calorimetry (DSC) to investigate the martensitic transformation. Mössbauer spectroscopy was used in retrodispersion geometry with the electron conversion technique (CEMS). Hyperfine parameters and phase fractions were obtained as a function of the Mn and Si. A discussion about the effect of the components on the magnetic states of both phases, g and e, is also performed. The enthalpy of transformation as a function of alloying elements was obtained from the DSC study of alloys and phase fractions obtained from Mössbauer spectra.