INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Si and Mn dependence of hyperfine parameters of Fe-Mn-Si shape memory alloys
J. MARTÍNEZ; S. M. COTES; J. DESIMONI
La Plata, Argentina
Conferencia; XI Latin American Conference on the Applications of the Mössbauer Effect; 2008
Fe-Mn based alloys with the addition of a third alloying element, in particular Si, have attracted considerable interest because of its technological applications related on the shape memory effect (SME) and on the economic convenience. The SME in these alloys is governed by the martensitic transformation between two metastable phases, gamma (austenite, fcc) and epsilon (martensite, hcp). Suitable direct and reverse transformation temperatures along with good mechanical and machining properties made the alloys good candidates for applications like couplings or for easy installation in difficult areas preventing the use of welding. It is well known that Si additions to the binary Fe-Mn system not only improve the SME but also the mechanical properties of the alloys. Si additions decrease Neel temperature, TN, of the gamma phase allowing a wider field of transformation temperatures and compositions were the gamma/epsilon takes place. The present study was performed for alloys belonging to the 15 to 30 at% Mn and 0 to 12 at% Si composition ranges. Alloys were melted several times in an arc furnace in order to improve homogenization and then received different thermal and surface treatments. As a result of the investigation the evolution and dependence with the Mn and Si contents of the hyperfine parameters of gamma and epsilon for phases have determined, producing the Si incorporation the most important variation of the hyperfine parameters. Moreover, the amount of transformed phase and its dependence with composition was also obtained and compared with results attained by dilatometric and calorimetric measurements. The discrepancies observed are discussed in relation with the density of stacking faults and the magnification of the used techniques.Some discrepancies between our results about TN and literature were found.