Microstructural characterization of oxide dispersion strengthened ferritic steel powder

Oxide dispersion strengthened ferritic steel powder was prepared by mechanical alloying of pre-alloyed ferritic steel powder together with nano Y2O3 in a dual drive planetary ball mill. A detailed investigation was carried out using X-ray diffraction, field emission electron microscopy and transmission electron microscopy. Microstructural parameters such as, crystallite size, lattice strain, deformation stress and dislocation character were evaluated using different Williamson–Hall models; uniform deformation model, uniform stress deformation model and modified Williamson–Hall model and the results obtained were compared and discussed. Uniform stress deformation model and modified Williamson–Hall model were observed to give better estimation of crystallite size as they consider strain anisotropy. With milling, dislocation character was observed to be changing, from near edge to mixed type. Lattice parameters of the milled powders were also estimated. Uniform milling with convoluted particle shape and homogeneous distribution of Y2O3 throughout the matrix was observed by using electron microscopy.