Quasi-Situ Characterization of Deformation in Low-Carbon Steel with Equiaxed and Lamellar Microstructure Treated by the
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Quasi‑Situ Characterization of Deformation in Low‑Carbon Steel with Equiaxed and Lamellar Microstructure Treated by the Quenching and Partitioning Process Pengfei Gao1,2 · Weijian Chen1,2 · Feng Li1,2 · Beijia Ning1,2 · Zhengzhi Zhao1,2 Received: 26 March 2020 / Revised: 15 June 2020 / Accepted: 5 July 2020 © The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The relationship between microstructure morphology and mechanical properties of the low-carbon steel (Fe-0.20C-2.59Mn2.13Si) treated by different intercritical annealed quenching and partitioning (Q&P) processes was investigated through interrupted tensile tests plus quasi-situ electron backscatter diffraction measurements. Results show that size and distribution of retained austenite (RA) directly affect the sequence of deformation induced martensitic transformation. As strain increases, the equiaxed RA grains wrapped by ferrite transform first, followed by the equiaxed and film-like RA grains adjacent to martensite. Compared with traditional intercritical annealed Q&P steel with equiaxed structure, the steel with quenching pretreatment contains uniform lamellar structure and the relatively film-like type of RA, leading to the higher yield strength, tensile strength, and elongation, as well as the steady increase in dislocation density upon straining. Keywords Steel · Quenching and partitioning · Austenite · Martensitic transformation · Electron backscatter diffraction (EBSD) · Tensile test
1 Introduction As a member of the third-generation advanced high strength steels (AHSS), the quenching and partitioning (Q&P) steel has gained full attention in recent decades [1–4]. Proposed by Speer et al. [5], the Q&P steel has a high elongation and an excellent strength-ductility balance. In particular, the intercritical annealed Q&P steel, which obtains better comprehensive properties, has realized industrial production [6]. The intercritical annealed Q&P heat treatment process prompts the low-carbon steel to form a multiphase Available online at https://link.springer.com/journal/40195 Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40195-020-01135-8) contains supplementary material, which is available to authorized users. * Zhengzhi Zhao [email protected] 1
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Beijing Laboratory of Metallic Materials and Processing for Modern Transportation, Beijing 100083, China
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microstructure, including ferrite, martensite, and retained austenite (RA). Numerous studies have focused on the effect of phase volume fractions and grain size on mechanical properties and the relationship between the stability of RA and transformation-induced plasticity (TRIP) effect [7–9]. Knijf [10] demonstrated that the morphological characteristics (equiaxed or lamellar) of microstructure had a significant influence on the mechanical properties. Many studie
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