Abstract
To address the growing demand and stringent requirements for lightweight steel, quenching and partitioning (QP) steel has attracted significant attention due to its excellent strength–ductility balance. However, to date, reports on the mechanism of intercritical annealing QP have been limited. Thus, this study investigated the effect of the addition of 1.3 wt% to 2.5 wt% Si on the microstructure and mechanical properties of intercritically annealed QP steel. Neutron diffraction and quasi-in situ electron backscatter diffraction were used to analyze the deformation mechanisms of commercial-grade QP1180 steel and Si-strengthened QP steel. The microstructure of the QP steel consisted of ferrite, martensite, and retained austenite (RA). Si increased the volume fractions of ferrite and RA. The Si-strengthened QP steel with a multiphase structure, including 43% ferrite, 13% RA, and 43% martensite, exhibited better tensile strength (1330 MPa), higher elongation (21.5%), and lower yield ratio (0.615) than commercial-grade QP1180 steel. The mechanical stability of larger RA grains is lower than that of finer grains. RA experienced additional stress with the ferrite yield and Si promoted interphase deformation accommodation behavior. The interphase deformation accommodation mechanism rather than the orientation-dependent mechanism plays a key role in controlling the onset of the deformation-induced martensite (DIM) transformation. Thus, the DIM transformation was triggered before the yield of RA, and the residual RA after the DIM transformation exhibited a non-negligible stress distribution.
| Original language | English |
|---|---|
| Article number | 112145 |
| Journal | Materials Characterization |
| Volume | 191 |
| DOIs | |
| State | Published - Sep 2022 |
Funding
This work was supported by the fellowship of China Postdoctoral Science Foundation [ 2021M690347 ] and the Key Research and Development Plan of Shandong Province [No. 2019TSLH0103 ]. This research used resource at Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). This work was supported by the fellowship of China Postdoctoral Science Foundation [2021M690347] and the Key Research and Development Plan of Shandong Province [No.2019TSLH0103]. This research used resource at Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
Keywords
- Deformation-induced martensite transformation
- Microstructure
- Neutron diffraction
- Quenching and partitioning steel
- Retained austenite