The Effect of Crystallinity on the Corrosion Behavior of SAM2x5 Amorphous Steel in situ Composite

SAM 2x5 is a Fe-based bulk metallic glass with a chemical composition of Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 which has a significantly higher corrosion resistance compared to its crystalline counterparts. In this research, dense samples were prepared using the spark plasma sintering technique at varying temperatures ranging from 630 to 675oC whose crystallinity percent changes from 20 wt.% to 82 wt.%. Corrosion rate of specimens was measured in a 3.5% NaCl solution. It was found that by enhancing sintering temperature and consequently crystallinity percent, the corrosion rate increases from 7.21 mpy (mils per year) to 15.75 mpy. Results of scanning electron microscope showed that there is no significant microstructural change in the amorphous matrix after corrosion test, while the crystalline regions are severely corroded. Although the corrosion rate increases with increasing percent crystallinity, it is still considerably lower than the control stainless steel sample which yields a corrosion rate of 28.93 mpy when studied under the same conditions