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Open AccessFeature PaperArticle

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

Department of Mechanical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Research and Development, ArcelorMittal Dofasco, Hamilton, ON L8H 3N8, Canada
Author to whom correspondence should be addressed.
Academic Editor: Richard Thackray
Materials 2017, 10(4), 346;
Received: 22 December 2016 / Revised: 14 March 2017 / Accepted: 24 March 2017 / Published: 27 March 2017
(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)
The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures. View Full-Text
Keywords: ductile failure; damage; voids; dual-phase steel; ferritic-bainitic steel ductile failure; damage; voids; dual-phase steel; ferritic-bainitic steel
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Pathak, N.; Butcher, C.; Worswick, M.J.; Bellhouse, E.; Gao, J. Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching. Materials 2017, 10, 346.

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