“Effect of ball milling on a hcp Fe-Mn solid solution”

A. F. CABRERA; S. M. COTES

Galerias Pacifico, Bs. As., Argentina

Congreso; 15th International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM’2008); 2008

FCC-FeMn alloys have been the object of study from decades ago because of their practical use. There exist such applications in shape memory clamps or in electronics as spin valves. It has became also an interesting academic research topic. The Fe-Mn phase diagram at atmospheric pressure indicates that the stable phase at room temperature is alfa-Fe(Mn), with BCC structure, and alfa-Mn(Fe), depending on Mn concentration. Traditional methods like fast quenching from high temperatures allowed us the Fcc-Fe(Mn) phase be obtained at room temperature. In particular, in the alloy with 19.3 wt%Mn of interest in this work, a martensitic transformation between FCC and HCP metastables phase had taken place during quenching and we have obtained only the HCP phase at room temperature. In this work we have explored the production of powder FCC-Fe(Mn) phase using ball milling. We departured from small pieces of quenched Fe-19.3wt%Mn alloy and milled for different times.The evolution of samples were monitored by Mössbauer spectroscopy at room and low temperatures, X-Ray diffraction, AC susceptibility and magnetic measurements were performed in a Physical Properties Magnetic System (PPMS). In this way, we have obtained an extensive characterization of the samples and found that the inicial HCP structure is destroyed by the milling, resulting an almost FCC powder with some traces of BCC phase. Finally, we discuss our results on the light of the induced chemical disorder.