Microstructure and Corrosion Properties of Fe-Cr-Si Alloys Prepared by Mechanical Alloying Method

The microstructure and corrosion properties of Fe-Cr-Si alloys prepared by mechanical alloying method were studied using the Fe-57 transmission Mossbauer spectroscopy (TMS), x-ray diffraction (XRD), and scanning electron microscope (SEM). The initial ternary mixture in Fe: Cr: Si atomic ratio of 85: 10: 5 was prepared on the basis of high-purity Fe, Cr, and Si powders. The studied samples were obtained after 10 h (MA-10h), 20 h (MA-20h), and 50 h (MA-50h) of alloying process in planetary ball mill. The SEM results indicate that the mean particle size of prepared material is strongly dependent on milling time and the estimated mean particle sizes were 15.4 (+/- 3.0) mu m, 9.0 (+/- 1.5) mu m, and 1.73 (+/- 23) mu m for MA-10h, MA-20h, and MA-50h, respectively. The XRD and TMS measurements reveal that all the prepared powders are alloys with body-centered cubic (bcc) structure. Moreover, TMS was used to investigate corrosion of Fe-Cr-Si powders during exposure to air at high temperature. The obtained results suggest that reduction of mean particle size of mechanically synthesized alloy drastically decreases its corrosion resistance properties. Finally, the hyperfine field distributions p(B) obtained for MA-10h, MA-20h, and MA-50h samples before and after annealing were compared with the simulated p(B) for a random bcc Fe0.85Cr0.10Si0.05 alloy. This comparison shows that the amount of Cr and Si atoms dissolved in Fe-Cr-Si bcc alloy changes significantly with time of mechanical alloying as well as with annealing.