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

Simone Kaar, Daniel Krizan, Reinhold Schneider, Coline Beal, Christoph Sommitsch

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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.
Original languageEnglish
Article number1122
JournalMetals
Volume9
Issue number10
DOIs
Publication statusPublished - 19 Oct 2019

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Steel
Manganese
Martensite
Austenite
Quenching
Elongation
Tensile strength
Mechanical properties
Microstructure
Scanning electron microscopy
Saturation magnetization
Ferrite
Deterioration
Ductility
Volume fraction
Stabilization
Cooling
Temperature

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Effect of Manganese on the Structure-Properties Relationship of Cold Rolled AHSS Treated by a Quenching and Partitioning Process. / Kaar, Simone; Krizan, Daniel; Schneider, Reinhold; Beal, Coline; Sommitsch, Christoph.

In: Metals, Vol. 9, No. 10, 1122, 19.10.2019.

Research output: Contribution to journalArticleResearchpeer-review

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abstract = "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.",
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