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Open AccessArticle

Effect of Manganese on the Structure-Properties Relationship of Cold Rolled AHSS Treated by a Quenching and Partitioning Process

1
Research and Development, University of Applied Sciences Upper Austria, Wels 4600, Austria
2
Research and Development Department, Business Unit Coil, voestalpine Stahl GmbH, Linz 4020, Austria
3
Institute of Materials Science, Joining and Forming, Graz University of Technology, Graz 8010, Austria
*
Author to whom correspondence should be addressed.
Metals 2019, 9(10), 1122; https://doi.org/10.3390/met9101122
Received: 17 September 2019 / Revised: 15 October 2019 / Accepted: 16 October 2019 / Published: 19 October 2019
The present work focuses on the investigation of both microstructure and resulting mechanical properties of different lean medium Mn Quenching and Partitioning (Q&P) steels with 0.2 wt.% C, 1.5 wt.% Si, and 3–4 wt.% Mn. By means of dilatometry, a significant influence of the Mn-content on their transformation behavior was observed. Light optical and scanning electron microscopy (LOM, SEM) was used to characterize the microstructure consisting of tempered martensite (α’’), retained austenite (RA), partially bainitic ferrite (αB), and final martensite (α’final) formed during final cooling to room temperature (RT). Using the saturation magnetization measurements (SMM), a beneficial impact of the increasing Mn-content on the volume fraction of RA could be found. This remarkably determined the mechanical properties of the investigated steels, since the larger amount of RA with its lower chemical stabilization against the strain-induced martensite transformation (SIMT) highly influenced their overall stress-strain behavior. With increasing Mn-content the ultimate tensile strength (UTS) rose without considerable deterioration in total elongation (TE), leading to an enhanced combination of strength and ductility with UTS × TE exceeding 22,500 MPa%. However, for the steel grades containing an elevated Mn-content, a narrower process window was observed due to the tendency to form α’final. View Full-Text
Keywords: lean medium Mn Q&P steel; stress-strain behavior; mechanical properties; retained austenite stability lean medium Mn Q&P steel; stress-strain behavior; mechanical properties; retained austenite stability
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MDPI and ACS Style

Kaar, S.; Krizan, D.; Schneider, R.; Béal, C.; Sommitsch, C. Effect of Manganese on the Structure-Properties Relationship of Cold Rolled AHSS Treated by a Quenching and Partitioning Process. Metals 2019, 9, 1122.

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