Impact of Martensite Spatial Distribution on Quasi-Static and Dynamic Deformation Behavior of Dual-Phase Steel
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FERRITE–MARTENSITE dual-phase (DP) steels are attracting a great demand in the automobile industries owing to their high strength-to-weight ratio, excellent formability, and high yield-to-ultimate strength ratio.[1,2] Moreover, being a potential material for the automobile component application, DP steels are studied extensively in order to evaluate and understand their plastic
MANPREET SINGH and TARUN NANDA are with the Mechanical Engineering Department, Thapar University, Patiala 147004, India. ANINDYA DAS, KRISHNENDU MUKHERJEE, MAHESH WALUNJ, and B. RAVI KUMAR are with the CSIRNational Metallurgical Laboratory, Jamshedpur 831007, India. Contact e-mail: [email protected] T. VENUGOPALAN is with Tata Steel Limited, Jamshedpur 831001, India. Manuscript submitted June 23, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
deformation characteristic in various loading conditions.[3–5] The difference in hardness of ferrite and martensite phases of DP steels provides various microstructure engineering opportunities in developing high-strength steels with excellent properties. Because of the complex microstructure (ferrite + martensite) constituents, the properties of DP steels are found to be influenced largely by the (a) volume fraction, (b) size and its distribution, and (c) morphology of the individual constituent phases.[6–10] Erdogan et al. reported that yield strength (YS) and ultimate tensile strength (UTS) increase for DP microstructure consist of fine martensite compared to blocky martensite in ferrite matrix.[11] On the other hand, martensite volume fraction noted to influence the ductility and the ductile void formation characteristics during plastic deformation.[12,13] Ductility was also found to be largely affected by the morphology of martensite. The fine fibrous or fine globular type martensite reported producing higher total elongation compared to coarser/
blocky type martensite.[13] Martensite morphology and its distribution were also reported to affect the fracture/damage mechanisms of DP steels.[14,15] In a recent work, Ravi et al.[16] produced a core–shell type martensite/ferrite DP microstructure by controlling austenite decomposition and found that microcracks initiated in martensite packets were arrested at the martensite/ferrite inter-phase boundaries. The network of ferrite channel around martensite retarded the crack growth and thereby delays the onset of global deformation. Therefore, ductility was found to increase in core–shell type morphology even with high volume fraction of martensite. All the above-discussed DP microstructure details enable one to understand the influence of microstructure parameters on mechanical properties of the DP steels. For automobile crashworthiness assessment, it becomes an absolute necessity to investigate the effect of these microstructure parameters on the deformation characteristics of DP steels at high strain rates. The typical strain rate of deformation experienced during an event of automobile crash is around 100 to 500 s 1. The effect of martensite volume fra
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