Structural and magnetic properties of grain boundaries inFe60Cr40 alloy synthesized by mechanical alloying

Mechanical alloying of iron and chromium powder mixtures was performed from 0 to 190 h milling times. X-ray diffraction, Mossbauer spectrometry and differential scanning calorimetry were used to determine the structural and magnetic properties of the intergranular zone, which was associated with a very disordered grain boundary structure, paramagnetic at 300 K. This structure is assumed to be due to the presence of oxygen and nitrogen atoms, forming a mixture of amorphous FeCr + O + N alloy. Between 21 and 85 h, the hyperfine parameters of the magnetic contribution, and therefore the properties of the Fe60Cr40 nanograin cores, are constant, but the paramagnetic fraction associated with the intergranular zone increases. At 85 h, the paramagnetic contribution represents 100% of the Mossbauer spectrum., Moreover, after very long milling times, we have evidenced a de-mixing reaction which results in preferential oxidation and nitrogenation within the very disordered structure.