Determination of Yield Stress in a Duplex Steel with α + γ Lamellar Structure

Abstract

Yield stress σ_y is evaluated in a duplex steel with α + γ lamellar structure by calculating the stress for the propagation of pile-up dislocations in one phase into another phase. Effective grain size of a lamella is determined to calculate the contribution of each boundary of a lamella to dislocation pile-up. Comparison of stresses required to drive α-to-γ and γ-to-α propagations of pile-up dislocations suggests that α + γ lamellar structure yields by propagation of pile-up dislocations in α lamella to γ lamella. σ_y of α + γ lamellar structure is calculated as the sum of friction stress σ_oα of α and the stress component Δσ_γ for yielding of γ lamella at the effective grain size d_α,eff of α lamella. The calculated results explain better to the experimental σ_y than do results calculated using rule of mixture.