grain sizes from 1.6 to 208μm to determine the effect ofgrain size on the strength, ductility and fracture. Both yield and flow stresses depend on grain size in agreement with a Hall-Petch relation when the specimen size effect is taken into account. The increase in Hall-Petch slope with strain is explained in terms of the difference in work-hardening rate for different grain sizes. The increase of lattice friction stress with strain is found to be analogous to the single crystal properties. While the {111} cracking is predominant without necking for coarse-grained specimens, the slant-type fracture and cup-cone fracture preceded by a necking is mainly observed for intermediate and finegrained specimens, respectively. Large elongation is developed when the intersection of slip bands becomes insufficient to produce the {111} cracking, and the void formation which results in the cup-cone fracture is retarded.