The Magnetic Aspects of the γ-α and γ- Martensitic Transformations in Fe-Mn Alloys

Fe,,Mn, alloys undergo fcc-bcc (y-a) and fcc-hcp (y-E) transformations for about 0<x<10 at % and 15<x<30 at% respectively. The product phase in the region 10<x<15 at. % is mixed a+€ and ~ + y . The y-a transformation in Fe-Mn is similar to that in Fe-rich Fe-Ni alloys where the transformation takes place between a high-temperature dense fcc structure and a lowtemperature more open bcc structure. This anomalous volume increase at the martensite transformation temperature is closely related to short-range ferromagnetic correlations in the fcc and bcc states. The y-E: transformation in Fe-Mn takes place between a high-temperature fcc structure and a relatively denser packed low-temperature hcp structure. In this case there is no anomalous volume increase.In the present work we investigate the volumetric properties of Felo0.,Mn, with x=830 at % and examine the influence of the magnetic properties on the y-a and y-E martensitic transformations. Results show that the y-E transformation occurs with the simultaneous loss of ferromagnetic correlations in the y-phase.