Diffusion Model-Guided Improvement of Chemical Homogeneity in Iron–Nickel Alloy Powder Synthesized by Solid-State Hydrogen Reduction

Abstract Any metal alloy powder synthesized by solid-state hydrogen reduction of metal oxides should be chemically homogeneous for direct conversion into a versatile product. In this study, a 50-wt.% Fe 2 O 3 -NiO powder mixture was reduced using hydrogen for 45 min at 700°C and homogenized in argon at 1100°C. The absence of oxygen in the as-reduced and homogenized powders was confirmed via exhaust gas analysis and X-ray diffractometry. Three homogenization times, 5, 10, and 15 h, were tested in experimental trials based on simulation results. Energy-dispersive X-ray spectroscopy in a scanning electron microscope revealed few iron-rich sites in the sample homogenized for 5 h, a predominance of iron in the sample homogenized for 10 h, and a homogeneous composition after 15 h of homogenization. The 15-h-homogenized powder exhibited relatively extensive neck growth and minimal porosity, indicating suitability for direct use. Iron- and nickel-free impurities from the Fe 2 O 3 feedstock were observed on and within powder particle boundaries. They were non-detrimental to the reduction and homogenization processes. These results demonstrate that solid-state reduction and homogenization at 1100°C for 15 h yield a microscopically homogeneous alloy powder, sinterable into a solid product. The findings are generalizable to other alloy systems and higher-order oxide mixtures.