Structural and thermal behaviors of iron-based gas-atomized powders
摘要
The present research is focused on the development of gas-atomized Fe-based amorphous alloy powders applicable for additive manufacturing of complex and critical shape components. The alloy of nominal composition Fe72.5B6Si3C4P10Cr2Mo2Mn0.5 (all in at%) was prepared as micron-sized powders by a gas atomizer (GA) under high pressure of nitrogen gas. After sieving analysis, the GA powders were separated in varying size ranges, and the particles of 25–93 μm size range were collected for further characterization. The X-ray diffraction pattern confirms a completely amorphous structure for powder particles up to 80 μm in size and crystallinity above 80 μm in size range powders. The powders of different size ranges represent the same glass transition temperature of 747 K and a little change in crystallization onset (801–804 K) and peak (804–806 K) temperatures with particle size. The powder particles above 80 μm in size require less activation energy for nucleation and growth of crystallites than those below that size range. The scanning electron microscopy of cross-sectional images reveals a featureless morphology in fine powders (40–55 μm), depicting its amorphous nature. In contrast, the coarser particles (~ 65 μm) represent the precipitation of crystallites in the amorphous matrix.