The effect of nitrogen on the glass-forming ability and micro-hardness of Fe-Cr-Mn-N amorphous alloys prepared by mechanical alloying

In this research, the effect of nitrogen on the thermal behavior and micro-hardness of Fe-Cr-Mn-N amorphous alloys synthesized by mechanical alloying under a nitrogen atmosphere has been considered. The characterization of the as-milled powders by X-ray diffraction, scanning and transmission electron microscopy showed that a fully amorphous structure has been developed by the mechanical alloying process. Differential scanning calorimetry results revealed that the glass transition temperatures and onset crystallization temperatures are in the ranges of 764-766 K and 855-861 K, respectively, for the alloys containing 3.45-3.95 wt.% nitrogen, giving considerable supercooled liquid regions of 91-95 K. The amorphous alloys exhibited an increase in the glass-forming ability by increasing the nitrogen amount. Furthermore, the as-milled amorphous powders showed high micro-hardness values of nearly 1015-1070 HV with an elastic-plastic deformation feature during the indentations. A decrease in the micro-hardness values was found by increasing the nitrogen content.