The effect of austenitization heat treatment on magnetic properties was examined by means of M?ssbauer spectroscopy on an Fe-40wt/Ni-2wt/Mn alloy. The morphology of the alloy was obtained by using scanning electron microscopy (SEM) under dif-ferent heat treatment conditions. The magnetic behavior of the non heat-treated alloy is ferromagnetic. A mixed magnetic structure including both paramagnetic and ferromagnetic states was obtained at 800°C after 6 and 12 h heat treatments. In addition, the magnetic structure of the heat-treated alloy at 1150°C for 12 h was ferromagnetic. With the volume fraction changing, the effective hyperfine field of the ferromagnetic austenite phase and isomery shift values were also determined by M?ssbauer spectroscopy.
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