On the Hall-Petch relationship and substructural evolution in type 316L stainless steel

Tensile specimens of Type 316L stainless steel having grain sizes in the range 3.1–86.7 μm were deformed to 34% strain at temperatures 24, 400 and 700°C and strain rate 1 × 10⁻⁴s⁻¹ to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development. Upto ∼5% strain the H-P relationship exhibits bi-linearity whereas the single Hall-Petch relation is exhibited at larger strains. The presence of bi-linearity is explained by the back stress associated with the difference in the dislocation densities in the vicinity of grain boundary and in the grain interior. The log stress (σ)-log strain (ε) plots depict three regimes and follow the relationship σ = Kεⁿ in each regime, but with varying magnitudes of the strength coefficient (K) and strain-hardening exponent (n).