Experimental and Numerical Analysis on Dual Phase Steel (DP780) Sheet Forming Limit and Effect of Microstructure Evoluti
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Experimental and Numerical Analysis on Dual Phase Steel (DP780) Sheet Forming Limit and Effect of Microstructure Evolution on Formability Bhargava Marrapu, Vivek Kumar Barnwal, Shanta Chakrabarty, Asim Tewari, and Sushil K. Mishra Submitted: 29 January 2020 / Revised: 12 September 2020 / Accepted: 27 September 2020 The application of dual phase steel in the automotive sector is increasing due to its high strength-to-weight ratio and good shock absorption capacity. The formability of dual phase steel is complex due to its multiphase microstructure which results in inaccurate formability prediction using numerical methods. The present study is aimed at analyzing the forming behavior and microstructure evolution of a dual phase steel, DP780, at different strain paths. The forming behavior of this steel was analyzed in terms of forming limit diagram (FLD) using Nakazima tests and finite element method. Various necking criteria were used to construct the FLD. Samples deformed at different dome height for three principal strain paths and strain levels were subjected to detailed microstructure and texture investigations. The microstructure and texture study was mainly focused on analyzing the development of deformation texture, misorientation development and orientation hardness. These studies showed that the formability of DP780 steel is largely affected by the development of c fiber texture. Also, the evolution of other microstructure and texture quantifiers such as texture intensity, misorientation and relative orientation hardness at different strain paths was correlated with the formability of the material. Keywords
dual phase steel, forming limit diagram (FLD), microstructure, necking, texture
1. Introduction Automotive industries are focusing on materials comprising high tensile strength and work hardening rate in addition to good formability for closure and structural applications (Ref 13). Hence, advanced high strength steel (AHSS), aluminum and magnesium alloys are the primary choices of materials for automotive industries (Ref 4-6). The main advantage of aluminum- and magnesium-based alloys is their low weight; however, the use of these alloys is limited by their low formability and mechanical properties (Ref 7). In contrast, AHSS alloys possess excellent combination of strength and formability. In addition, these alloys also have very good shock absorption properties. Dual phase (DP) steels, designated as first generation AHSS alloys with tensile strength of 5001200 MPa and total elongation of 12-34%, are extensively used for automotive parts (Ref 8, 9). A wide range of alloying Bhargava Marrapu, Asim Tewari, and Sushil K. Mishra, Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India; Vivek Kumar Barnwal, Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India; and Graduate Institute of Ferrous Technology, Pohang University of Science and Technology (POSTECH), 77 Cheongamro, Na
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