High-Speed Tensile Deformation Behavior of a Metastable 18Cr–6Ni–0.2N–0.1C Steel

Abstract

The present study investigated the high-speed deformation behavior of 6Ni–0.2N–0.1C steel. 0.2% proof stress (0.2% PS) of the 6Ni–0.2N–0.1C steel increased with an increase in strain rate () but tensile strength (TS) indicated almost the same value at above 10⁻¹ s⁻¹. Uniform elongation (U.El) largely decreased with an increase in . TS and U.El of the 6Ni–0.2N–0.1C steel at 10³ s⁻¹ were almost the same as those of SUS304 steel. When the effect of on mechanical properties was compared between the 6Ni–0.2N–0.1C and SUS304 steels, the strain rate dependence on 0.2% PS was larger in the 6Ni–0.2N–0.1C steel and that on TS was different at above 10⁰ s⁻¹. And the decrease of U.El with an increase in was larger in the 6Ni–0.2N–0.1C steel. The decrease of U.El at 10³ s⁻¹ was discussed from the viewpoint of change of flow stress at the maximum load point with an increase in . The estimated results proposed that austenite phase hardly transformed into deformation-induced martensite (α′) up to the maximum load point at 10³ s⁻¹ in the 6Ni–0.2N–0.1C steel. The tensile properties of the 6Ni–0.2N–0.1C steel are largely influenced by the higher strength of α′. It is difficult for the 6Ni–0.2N–0.1C steel to produce TRIP effect at high strain rates because the deformation-induced martensitic transformation is suppressed.