Studies on alloying process of Ni-20Cr-20Fe-0.6Y2O3 powders during mechanical alloying

In the present work, Ni-20Cr-20Fe-0.6Y2O3 oxide dispersion strengthened (ODS) nickel-based alloy powders were prepared by the mechanical alloying of elemental powders in a high energy attritor mill. XRD studies indicated that a single phase solid solution was obtained at 16 h of milling. The crystallite size of the milled powder decreased significantly while lattice-strain and lattice parameter increased with milling time. After 10 h of milling, a drop in lattice strain appeared due to dynamic recrystallization. The occurrence of dynamic recrystallization has been attributed to a reduction in strain rate and crystallite size and the rise in localized high-temperature. The size of yttria (Y2O3) refined and uniformly dispersed into the gamma matrix as the milling progressed which was confirmed by TEM observations. During subsequent annealing of the 16 h milled powders a considerable grain growth occurred on a nanocrystalline scale beyond 800 °C (35.5 nm) till 1100 °C(139 nm) while nanocrystallinity (<100 nm) was retained upto 1000 °C (96.5 nm).