Microstructural and hardness evolution of mechanically alloyed Fe-Cr-Mn-N powders

The effect of milling time on the structure and hardness of Fe-18Cr-4Mn-xN alloy powders processed by mechanical alloying is investigated. According to X-ray diffraction and transmission electron microscopy evaluations, complete amorphization is achieved beyond 126 h of milling. That is, the powders milled for the shorter durations are nanocrystal dispersed amorphous matrix composites. Microindentations on the as-milled powders reveal that the hardness of the nanocomposites first increases and then decreases by the amorphization progression. However, the hardness of the fully amorphous alloys progressively decreases by increasing the milling time.