Abstract
Quenching and partitioning (Q&P) and a novel combined process of hot straining (HS) and Q&P (HSQ&P) treatments have been applied to a TRIP-assisted steel in a Gleeble®3S50 thermomechanical simulator. The heat treatments involved intercritical annealing at 800 °C and a two-step Q&P heat treatment with a partitioning time of 100 seconds at 400 °C. The “optimum” quench temperature of 318 °C was selected according to the constrained carbon equilibrium (CCE) criterion. The effects of high-temperature deformation (isothermal and non-isothermal) on the carbon enrichment of austenite, carbide formation, and the strain-induced transformation to ferrite (SIT) mechanism were investigated. Carbon partitioning from supersaturated martensite into austenite and carbide precipitation were confirmed by means of atom probe tomography (APT) and scanning transmission electron microscopy (STEM). Austenite carbon enrichment was clearly observed in all specimens, and in the HSQ&P samples, it was significantly greater than in Q&P, suggesting an additional carbon partitioning to austenite from ferrite formed by the deformation-induced austenite-to-ferrite transformation (DIFT) phenomenon. By APT, the carbon accumulation at austenite/martensite interfaces was observed, with higher values for HSQ&P deformed isothermally (≈ 11 at. pct), when compared with non-isothermal HSQ&P (≈ 9.45 at. pct) and Q&P (≈ 7.6 at. pct). Moreover, a local Mn enrichment was observed in a ferrite/austenite interface, indicating ferrite growth under local equilibrium with negligible partitioning (LENP).
| Original language | English |
|---|---|
| Pages (from-to) | 4809-4823 |
| Number of pages | 15 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 49 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 1 2018 |
Funding
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, world-wide 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/dow nloads/doe-public-access-plan). Manuscript submitted January, 20 2018. Article published online June 28, 2018 The authors gratefully acknowledge financial support from CAPES—(Process No. 1715938), CNPq—Processes 401472/2012-4 and 235297/2014-3, Sandwich, Ph.D. The Brazilian Synchrotron Light Laboratory (LNLS) and Brazilian Nanotechnology National Laboratory (LNNano) are also acknowledged for the use of the XTMS facility; Arthur Seiji Nishikawa for valuable comments and discussions; and Dorothy W. Coffey for FIB (Focus Ion Milling) specimen preparation. The authors also thank Andres E. Marquez Rossy for help with the FEG-SEM. This research was performed, in part, using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities. APT measurements were conducted at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The authors gratefully acknowledge financial support from CAPES?(Process No. 1715938), CNPq?Processes 401472/2012-4 and 235297/2014-3, Sandwich, Ph.D. The Brazilian Synchrotron Light Laboratory (LNLS) and Brazilian Nanotechnology National Laboratory (LNNano) are also acknowledged for the use of the XTMS facility; Arthur Seiji Nishikawa for valuable comments and discussions; and Dorothy W. Coffey for FIB (Focus Ion Milling) specimen preparation. The authors also thank Andres E. Marquez Rossy for help with the FEG-SEM. This research was performed, in part, using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities. APT measurements were conducted at ORNL?s Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. 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, world-wide 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). Manuscript submitted January, 20 2018.