Characterization of mechanically alloyed Fe–Cr–Sn alloys

Abstract

Ferritic steels with high Cr concentration are extensively used due to their resistance to corrosion, also they are much cheaper to produce than Ni alloys and austenitic stainless steels. However, the formation of the sigma phase and phase separation affect their mechanical properties deleteriously. The addition of Sn to the Fe–Cr system retards the sigma phase formation. Their mechanical properties may be further improved by decreasing the average grain size and the density of defects inside the grains, as in nano-grained Fe–Cr alloys. Nanocrystaline Fe–Cr–Sn alloys, which are prepared by mechanical alloying, are thus, worthy of investigation. In this work mechanical alloying of mixtures of elemental Fe, Cr and Sn powders was carried out in an Ar atmosphere using either untreated or hardened vials and balls, in order to obtain the following alloys: Fe 55- x Cr 45Sn x with x = 0, 3 and 6 at%. These were studied by 57Fe Mössbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). It was found that the increasing of the Sn concentration leads to a reduction of particle size and grain size. Furthermore, milling in the untreated vials causes a partial amorphization of the alloys. Contamination from the balls and vials decreases with the increasing Sn concentration.