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 mu m were deformed to 34% strain at temperatures 24, 400 and 700 degrees C and strain rate 1 x 10(-4) s(-1) to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development. Up to similar to 5% strain the H-P relationship exhibits bi-linearity whereas the single Hall-Fetch 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 (sigma)-log strain (epsilon) plots depict three regimes and follow the relationship sigma = K epsilon(n) in each regime, but with varying magnitudes of the strength coefficient (K) and strain-hardening exponent (n).