GRAIN-GROWTH IN NANOCRYSTALLINE IRON PREPARED BY MECHANICAL ATTRITION

The grain growth in nanocrystalline Fe produced by high energy ball mi lling is investigated. Grain growth data are analysed using two differ ent models of grain growth, one of which takes pinning forces on the g rain boundaries into account. The grain growth exponents n from D-l/n - D-o(l/n) = kt for nanocrystalline and conventional polycrystalline F e are compared. The use of the above mentioned equation yields an acti vation energy of 125 kJ/mol, while the second model gives 248 kJ/mol. These Values are compared to those for grain boundary and lattice diff usion in Fe. Some evidence for two different sets of mechanisms govern ing the grain growth in nanocrystalline Fe are discussed. (C) 1997 Act a Metallurgica Inc.