The process and mechanisms for the transformation of coarse grain to nanoscale grain in tungsten by ball milling

The graphical abstract shows the schematic diagram of grain refinement process in powder and it includes four stages: (1) formation of large long stripe tungsten grains, (2) formation of medium-sized tungsten grains, (3) formation of small angle grain boundaries and (4) formation of small-sized tungsten grains. Nanocrystalline powder with average grain size smaller than 10 nm was obtained. Minimum grain size of 5 nm predicted by theory in tungsten powder was obtained after 60 h ball milling.492