Deformation mechanisms and microplasticity of austenitic TRIP/TWIP steel under flyer plate impact

¹ Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, Germany
² Institute of Materials Science, Technische Universität Bergakademie Freiberg, Germany
³ Russian Academy of Sciences, Institute of Problems of Chemical Physics, Chernogolovka, Moscow Region 142432, Russia

^* Corresponding author: ralf.eckner@iwt.tu-freiberg.de

Published online: 7 September 2018

Abstract

Abstract. The focus of this study is on the deformation mechanisms of high-alloy cast austenitic TRIP/TWIP steel with the nominal composition Fe-16Cr-6Mn-6Ni. Due to its chemical composition, the material exhibits a low stacking-fault energy of 17.5 mJ/m² which facilitates the formation of the deformation-induced γ (fcc) → ε (hep) → α’ (bcc) transformation. Consequently, the steel exhibits a tensile strength of 800 MPa with fracture elongation of 55 % under quasi-static loading. The experiments presented demonstrate the response of this steel to flyer-plate impact (FPI) at room temperature using two different test setups. In the first setup, laser interferometry measurements of the sample free surface were used for determination of the dynamic mechanical properties (Hugoniot elastic limit / HEL. spall strength) after impact with aluminium plates accelerated up to 650 m/s. In the second setup, an experimental shock testing device developed at the Freiberg High-Pressure Research Centre was used for impacting large cylindrical samples without the occurrence of spallation. Subsequently, microstructural investigations were carried out by scanning electron microscopy (SEM) and transmission election microscopy (TEM) in combination with diffraction techniques and magnetic martensite measurements. Their results facilitate the representation of a complete image of deformation mechanisms during shock wave loading.