Structural and compositional changes during mechanical milling of the Fe–Crsystem

Abstract

The structural and compositional changes during mechanical milling of Fe–Cr powder(10 wt% Cr) were followed by scanning electron microscopy (SEM), atomic forcemicroscopy (AFM), x-ray diffraction (XRD), Mössbauer spectroscopy and magnetizationmeasurement. All these techniques give complementary information about the alloyingprocess during milling. Different particles are cold welded and elongated to formcomposite granules in the initial stage of milling (5–10 h). The crystalline order isalso destroyed heavily and nanosize crystallites are formed during early milling.Chromium diffusion in the iron lattice starts somewhat late (after 20 h of milling) whencomposite granules flatten, reducing the distance between iron and chromium layers.Though compositional homogeneity is achieved up to nanometre scale in 65 hof milling, atomic diffusion of the species still continues up to 100 h of milling.