The strain-rate dependence of the Hall-Petch effect in two austenitic stainless steels with different stacking fault energies

Using thermal-mechanical treatments, specimens with different grain sizes were produced for two Cr-Ni-based austenitic stainless steels with different stacking fault energies (analogues of AISI 316L and AISI 321 steels). The effect of strain-rate on the tensile deformation behavior and strength properties was evaluated for these steels. In given grain size interval, (3-73)mu m for 316 steel and (0.2-32)mu m for 321 steel, the yield strength sigma(0.2) varies with grain size 1) in accordance with Hall-Petch relationship sigma(0.2) = sigma(0) + k(HP)D(-1/2). The Hall-Petch coefficient k(HP) depends on steel composition (stacking fault energy) and possesses higher value for 321 steel as compared to 316 steel. Increase in strain-rate in the interval of 1.0 x 10(-4) s(-1) to 1.0 x 10(-2) s(-1) causes growth in stress sigma(0), but weakly changes coefficient k(HP) in Hall-Petch relationship: 322-327 MPa x m(0.5) for 316 steel and 404-413 MPa x m(0.5) for 321 steel. The strain-rate dependence of the constants in Hall-Petch relationship was discussed in terms of deformation mechanism and dislocation arrangement in both steels.