Plastic flow phenomenology of 304L stainless steel

Abstract

The isothermal plastic flow behavior of annealed 304L austenitic stainless steel in uniaxial compression and torsional modes of deformation has been established over a wide range of temperatures and strain rates. In uniaxial compression, it was found that high rates of strain hardening, which persist to large strains (≽.7) at cold-working temperatures, are found only at small values of strain (⪯0.2) at hot-working temperatures because of the influence of dynamic softening processes. The effect of deformation heating on flow behavior, which occurs primarily at high strain rates, was most significant at cold-working temperatures. Deformation heating was observed to result in flow stress maxima and flow softening. A method of estimating high-strain rate, isothermal-flow curves in such instances was derived. Shear stress-shear strain curves derived from torsion tests exhibited dependences on temperature and strain rate similar to those observed in compression data. In contrast to the compression curves, however, the shear stress-shear strain curves showed lower rates of strain-hardening at room temperature, 400 °C, 800 °C, and (for high strain rates) 1000 °C. It was shown that the choice of definition for calculating effective stress-strain from the torsion data could not be modified to bring the two types of data into coincidence. Only a structure-sensitive explanation could be invoked to explain the difference.