Effect of Strain Rate on the Yield Stress of Ferritic Stainless Steels

The effect of strain rate on the yield stress of ferritic stainless steel sheet was experimentally determined and a previously developed model was applied to the data. Five ferritic stainless steel alloys, including one in two thicknesses, were mechanically tested at room temperature in uniaxial tension at strain rates ranging from 0.001 to 300 s⁻¹, and low-strain-rate tests were selectively performed at nonambient temperatures. The hypothesis that ferritic stainless steels react similarly to strain rate as mild steels was investigated by the application of a widely accepted strengthening model, based on body-centered-cubic (bcc) crystal lattice deformation mechanisms, to the experimental data.[1] Yield stresses were compared to model predictions and good agreement was found. The results allow for the prediction of yield stresses for these materials over strain rate ranges of 0.001 to 300 s⁻¹, and as a function of test temperature. Model parameters for the ferritic stainless steels were reasonable relative to those previously reported for pure bcc ferritic iron.[1] A correlation between the effect of alloying additions on solid solution strengthening and the athermal component of shear stress is also suggested. The results allow prediction of yield stress of ferritic stainless steels over a wide range of strain rates and temperatures.