Initiation of Dynamic R Initiation of Dynamic Recry ecrystallization of As-Cast N08028 Allo stallization of As-Cast N08028 Alloy Elena Mora, Aitor Navarro, Elena Silveira, Cecilia Poletti, Joseba Mendiguren and Iñaki Hurtado Elena Mora. Department of Mechanical and Industrial Production, Mondragon Unibertsitatea, Loramendi 4, Mondragon 20500, Gipuzkoa, Spain Corresponding author: emora@mondragon.edu Aitor Navarro. Tubacex Innovación AIE, Parque Científico y Tecnológico de Bizkaia, Astondo Bidea, Edificio 702, Derio, Bizkaia, Spain Elena Silveira. Tecnalia, Parque Tecnológico de San Sebastian, Mikeletegi Pasealekua, 2, 20009 Donostia-San Sebastián, Gipuzkoa, Spain Cecilia Poletti. Institute of Materials Science, Joining and Forming at Graz University of Technology, Kopernikusgasse 24/I, 8010 Graz, Austria Joseba Mendiguren. Department of Mechanical and Industrial Production, Mondragon Unibertsitatea, Loramendi 4, Mondragon 20500, Gipuzkoa, Spain Iñaki Hurtado. Department of Mechanical and Industrial Production, Mondragon Unibertsitatea, Loramendi 4, Mondragon 20500, Gipuzkoa, Spain Abstr bstract act. The use of high nickel content austenitic stainless steels (SASS) has significantly increased in the last decade. The corrosion and high fatigue resistance of these materials make them suitable for manufacturing oil country tubular goods (OCTG). SASS are processing by forging from casting conditions. Dynamic recovery (DRV) and recrystallization (DRX) of as-cast super austenitic stainless steel, N08028 Alloy, is investigated to study the refining effect from the as-cast grain structure to fully recrystallized austenite due to hot deformation. Both the critical stress and strain for the initiation of DRX are determined using the flow curves. To perform this analysis, hot compression tests are performed at temperatures between 900°C and 1250°C, and strain rates between 0.1 s -1 and 10 s -1 , up to 0,8 final strain using a Gleeble®3800 thermomechanical simulator. Subsequently, the Johnson-Avrami-Mehl-Kolmogorow (JMAK) model is used to numerically fit the flow curves and consequently determine the critical strain. No critical points are seen for temperatures under 1100°C. Above this temperature, the JMAK model proves to be valid in all studied strain rates. Keyw ywor ords ds. Critical Strain, Dynamic, Recrystallization, Austenitic Stainless Steel, Hot Compression Test 1 Intr 1 Introduction oduction N08028 Alloy is widely used in chemical and petrochemical industry due to its excellent corrosion resistance and its large yield strength [1]. Its workability is poor and the hot working range is narrow. During thermos-mechanical treatments dynamic recovery (DRV) and dynamic recrystallization (DRX) are the most important restoration mechanisms. They affect the final microstructure and, therefore, the mechanical properties. The hot deformation behavior of the Alloy N08028 during a hot extrusion process was studied by Wang et al. [2], who found that this alloy undergoes DRX due to its low stacking fault energy of N08028 Alloy [3]. However, the stacking fault energy varies depending on the initial state of the material. Huiqin et al. [4] studied for the Mn18Cr18N stainless steel, and compared the activation energy for both as-cast and wrought starting structures, concluding that the as-cast samples presents a higher energy than the wrought samples. Significant differences exist between as-cast ingots and as-forged billets. These include the grain sizes, morphologies, and solidification textures. These factors, strongly affect the hot-working ability, microstructural evolution, and mechanical properties of the final material [5]. Hence, it is important to investigate the critical conditions of DRX initiation of as-cast SSAS alloys during hot working. ESAFORM 2021. MS04 (Forging & Rolling), 10.25518/esaform21.896 896/1