Modified stress-strain relation for FCC metals and alloys

Abstract

The flow curve of some metals in the region of uniform plastic deformation can be expressed by the Ludwik model, σ=K∈ⁿ. For stable austenitic stainless steels and other face-centered-cubic (fcc) metals with low stacking fault energies, a second term has been added to the Ludwik model to account for devitations at low strains. The modified model $\sigma = K_1 \in ^{n_1 } + e^{K_2 } \cdot e^n e^ \in$ adequately describes the plastic flow of these materials. The value for σ at ε=0 in this model ise ^K ₂ and agrees reasonably well with the observed proportional limit. It is hypothesized that the modification term accounts for transient planar flow of dislocations favored by low stacking fault energy.