TY - JOUR

T1 - Austenite decomposition and carbon partitioning during quenching and partitioning heat treatments studied via in-situ X-ray diffraction

AU - Ebner, Sandra

AU - Suppan, Clemens

AU - Stark, Andreas

AU - Schnitzer, Ronald

AU - Hofer, Christina

PY - 2019

Y1 - 2019

N2 - High strength combined with excellent ductility can be achieved by quenching and partitioning (Q&P) microstructures containing martensite and a considerable amount of retained austenite. Since the mechanical properties are inherited from the microstructure, a thorough understanding of this relationship is indispensable. In the present work, in-situ synchrotron X-ray diffraction was used to investigate the transformation kinetics during Q&P processing. The effect of different heat treatment conditions on the microstructural evolution was examined and correlated to the mechanical properties obtained by tensile testing. The results showed that austenite decomposition occurred for all Q&P cycles, especially at the beginning of partitioning. The extent of this decomposition was affected by a change of the quenching temperature, while the partitioning temperature showed no significant influence. Regardless of the heat treatment parameters, carbon partitioning was clearly visible during the 2-step cycles, which led to enhanced work hardening with increasing strain. In contrast, this was not observed in the case of 1-step processing due to negligible carbon diffusion, and thus insufficient chemical stabilization of the austenite.

AB - High strength combined with excellent ductility can be achieved by quenching and partitioning (Q&P) microstructures containing martensite and a considerable amount of retained austenite. Since the mechanical properties are inherited from the microstructure, a thorough understanding of this relationship is indispensable. In the present work, in-situ synchrotron X-ray diffraction was used to investigate the transformation kinetics during Q&P processing. The effect of different heat treatment conditions on the microstructural evolution was examined and correlated to the mechanical properties obtained by tensile testing. The results showed that austenite decomposition occurred for all Q&P cycles, especially at the beginning of partitioning. The extent of this decomposition was affected by a change of the quenching temperature, while the partitioning temperature showed no significant influence. Regardless of the heat treatment parameters, carbon partitioning was clearly visible during the 2-step cycles, which led to enhanced work hardening with increasing strain. In contrast, this was not observed in the case of 1-step processing due to negligible carbon diffusion, and thus insufficient chemical stabilization of the austenite.

UR - http://www.scopus.com/inward/record.url?scp=85066013012&partnerID=8YFLogxK

U2 - 10.1016/j.matdes.2019.107862

DO - 10.1016/j.matdes.2019.107862

M3 - Article

VL - 178.2019

JO - Materials and Design

JF - Materials and Design

SN - 0261-3069

IS - September

M1 - 107862

ER -