Place: International Conference on Plasticity, St. Thomas (VI), USA
Grain refinement during severe plastic deformation is commonly used as a method to produce sub-micron and nanocrystalline material. In experimental studies it has been shown that surface attrition treatment can result in nanocrystalline grain structures close to the surface . In the present work large-scale atomistic simulations are used to study the effect of severe plastic deformation of surface layers on the evolution of the grain structure in ductile metals. The simulations reveal that during the plastic deformation new grains are being nucleated, while at the same time deformation induced grain growth occurs. Successive grain refinement by sub-grain formation is, however, not observed on the atomistic length and time scales. Hence, the presentation will focus on the fundamental mechanisms and critical states for grain nucleation and grain growth. The understanding of these micromechanisms leads to qualitative conclusions on the dynamic equilibrium between grain nucleation and grain growth, which depends on initial grain size and defect density, plastic strain rate and temperature.
References:  H.W. Zhang, Z.K. Hei, G. Liu, J. Lu, and K. Lu, Acta Materialia 51 (2003) 1871–1881.