Lach et al./Deformation Behavior of Nitrogen-Alloyed Austenitic Steels at High nounced with increasing hardness. The difference in strength between specimens 3 and 4 amounts to 200 MPa in Figure 4 and 500 MPa in Figure 5.
A metallographic study on quasistatically compressed specimens shows localized plastic deformation, the internal compression cone is distributed heterogeneously in the cross section. [8] Suppressed cross slipping of dislocations can be made responsible for this behavior. Quasistatic compression tests using cold-drawn and strain-aged steel P900N (curve 2, Fig. 4 and Fig. 5) result in a slightly decreased flow curve compared to curve 1 in Fig. 4 and Fig. 5. Metallographic investigation showed that plastic deformation is extremely localized in a narrow isothermal shear-band across the entire specimen. [8] The specimen rapidly looses its macroscopic cylindrical shape and the compression flow curve becomes irregular, because in the equation to evaluate the test data, it is assumed that specimens will stay cylindrical.
Nitrogen-alloyed austenitic steels are very strain-rate sensitive materials. Under solution-annealed conditions the dynamic compression strength is twice that of the quasistatic strength. From 430 HV30 onwards, cold work-hardened specimens tested dynamically show adiabatic shear-bands. Work-hardening at 400 C prior to testing increases the ductility of the material. The plastic deformation is localized in heavily work-hardened samples. ±