Abstract
The mechanism of nano grain formation in tungsten by mechanical milling, which is one of the methods for severe plastic deformation, was investigated. The powder microstructure was divided in some layered grain structures, and finally consisted of equiaxed nano grains. This nano grain structure was formed by the subdivision of the layered grain. These nano grains have non-equilibrium grain boundary structure. It is considered that such a specific microstructure is formed by extremely heavy plastic deformation by due to the mechanical milling process.
