Flow behavior and microstructures of large-grained Fe3Si during high temperature deformation

Fe3Si polycrystals having a large initial grain size of about 92 mum exhibit a large tensile elongation exceeding 200% at 1173 K and at 4.68x10(-4) s(-1). A stress-strain curve corresponding to the large tensile elongation is characterized by a steady state flow after an initial work hardening at a small plastic strain until final fracture. The apparent activation energy and strain rate sensitivity index is estimated to be 120 kJ/mol and 0.30, respectively. The deformation microstructure responsible for the large elongation consists of a well-defined subgrain microstructure with a low dislocation density within dynamic recrystallization (DRX) grains evolved during high temperature deformation. Large elongation is achieved by glide motion of (001) type dislocations. It is suggested that glide and climb motion of (001) type dislocations leads to simultaneous and/or alternate occurrence of DRX and dynamic recovery (DRV), which retards the initiation of plastic instability and results in large elongation. (C) 2002 Elsevier Science B.V. All rights reserved.