Effect of the Temperature of Shock-Wave Loading on Structure and Phase Transformations in Nitrogen-Containing Austenitic

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CTURE, PHASE TRANSFORMATIONS, AND DIFFUSION

Effect of the Temperature of Shock-Wave Loading on Structure and Phase Transformations in Nitrogen-Containing Austenitic Cr–Mn–Ni Steel V. V. Sagaradzea, *, N. V. Kataevaa, I. G. Kabanovaa, S. V. Afanaseva, and A. V. Pavlenkob aMikheev

Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, Ekaterinburg, 620108 Russia Russian Federal Nuclear Center, Zababakhin All-Russia Research Institute of Technical Physics, Snezhinsk, Chelyabinsk oblast, 456770 Russia *e-mail: [email protected]

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Received February 10, 2020; revised March 9, 2020; accepted March 10, 2020

Abstract—This work has determined the peculiarities of structure and phase transformations at various initial temperatures (–129…548°С) and high deformation rates (448–530 m/s) of shock-wave loading in the austenitic nitrogen-containing steel KH20N6G11M2AFB (0.4N–20Сr–6Ni–11Mn–2Mo–V–Nb). The cyclic γ → ε → γ transformation is observed in the course of shock-wave loading at 20–203°С, which causes the phase naklep of austenite and the possible occurrence of the shape memory effect in the regions of deformation localization. Keywords: austenitic steel, shock-wave loading, ε-martensite, electron microscopy, structure, deformation temperature DOI: 10.1134/S0031918X20070091

INTRODUCTION After various strengthening treatments, nitrogencontaining stainless steels, e.g., 0.4N–20Сr–6Ni– 11Mn–2Mo–V–Nb (Kh20N6G11M2AFB), [1–6] exhibit not only enhanced strength but also high resistance to pitting corrosion and corrosion cracking under loading in seawater. This allows them to be used as construction materials for hulls of marine vessels and marine constructions. Such steels can be used as cladding material for icebreaking ships [6], because of their high wear resistance [7] in an ice environment, as well as enhanced corrosion and mechanical properties [8–11]. Significant strength of these austenitic steels can be provided not only by the formation of the nitrogen-containing solid solution, but also dispersion hardening with the partial precipitation of local nanosized precipitates of nitrides, as well as the increased density of dislocations after high temperature thermomechanical treatment, cold and warm deformation [11]. In the course of the operation of icebreaking-ship hulls in ice fields, they are subjected to both friction and large shock loading. Intensive deformation can cause the formation of martensite phases in various steels [12–18]. The effect of intensive shock loading on the structure and phase transformations of nitrogen-containing steels at various temperatures has not been fully investigated. This work is devoted to the study of effects of shock-wave loading on the structure

and phase transformations in the nitrogen-containing Cr–Mn–Ni steel at various temperatures, including temperatures below 0°С. MATERIALS AND METHODS OF INVESTIGATION The nitrogen-containing austenitic steel 0.4N–20С– 6Ni–11Mn–2Mo–V–Nb (Kh20N6G11M2AFB) with 0.04 wt. % carbon was studied. Samples 35 mm in diameter and appr