Advanced High Strength Steels V: Session I
Sponsored by: TMS Structural Materials Division, TMS: Steels Committee
Program Organizers: Ana Araujo, Vesuvius USA; Louis Hector, General Motors Global Technical Center; Igor Vieira, Nucor Steel; Lijia Zhao, ArcelorMittal USA; Krista Limmer, Devcom Army Research Laboratory; Jonah Klemm-Toole, Colorado School of Mines; Sebastien Allain, Institut Jean Lamour; MingXin Huang, University of Hong Kong
Monday 8:30 AM
March 15, 2021
Room: RM 6
Location: TMS2021 Virtual
8:30 AM
Ferrite Recrystallization Investigated by In Situ High Energy X-ray Diffraction Experiments: Clelia Couchet1; Sébastien Allain1; Julien Teixeira1; Marc Moreno2; Guillaume Geandier1; Frédéric Bonnet3; 1Institut Jean Lamour; 2Transvalor S.A.; 3ArcelorMittal
Competitive recovery and recrystallization of a conventional low carbon ferritic steel have been investigated in situ thanks to High Energy X-Ray Diffraction experiments and original automated spot detection and tracking methods. These experiments has been carried out on P07 beamline in PETRA III at DESY (Hambourg) with a monochromatic beam (100 keV). High flux from synchrotron source and fast high-throughput 2D detector (Perkin-Elmer) collects Debye-Scherrer (DS) diffraction patterns at significant rate (10hz). Four isothermal annealing temperatures (450°C, 500°C, 550°C and 650°C) have been studied. Recovery kinetics has been determined using a modified Williamson-Hall method inspired by Ungar et al. (Appl. Phys. Lett. 69, 3173 (1996)) and compared to the prediction of recovery models. Recrystallization has been followed by tracking isolated diffraction spots on DS rings produced by newly recrystallized grains. This work aims to provide better understanding for recovery and recrystallization processes, both influencing final mechanical properties of steels.
8:50 AM
Carbon Content in Carbide-free Bainite during Isothermal Transformations: Irina Pushkareva1; Babak Shalchi-Amirkhiz1; Sebastien Allain2; Guillaume Geandier2; Frédéric Danoix3; Fateh Fazeli1; Matthew Sztanko1; Colin Scott1; 1CanMet Materials - Natural Resources Canada; 2Institut Jean Lamour; 3Groupe de Physique des Matériaux
Even if carbide-free bainitic steels are now used in many applications for automotive construction (crankshafts, stamped parts), the nature of the bainitic transformation remains a bone of contention among metallurgists. In this study, we have coupled three different experimental techniques to understand carbon partitioning between austenite, bainite and possibly carbides during their transformation in isothermal conditions. The carbon contents were determined by in situ High-Energy XRay Diffraction experiments on synchrotron beamlines using precise mass balances enabled by the techniques as well as using the phase tetragonality. Direct measurements by Electron Energy Loss Spectroscopy and 3D Atom Probe Tomography have also been conducted ex situ in bainite laths at room temperature. For the studied conditions and compositions (Fe0.2%C2.2%Mn1.5%Si+Mo/V), the values found in bainite laths are about 0.1%C meaning that a large fraction of carbon is not available for austenite stabilization.
9:10 AM
Dislocation Densities during Martensite Transformation in a Low-carbon Steel Determined by In Situ High Energy X-ray Diffraction: Juan Macchi1; Steve Gaudez1; Guillaume Geandier1; Julien Teixeira1; Sabine Denis1; Frédéric Bonnet2; Sébastien Allain1; 1Institut Jean Lamour; 2ArcelorMittal Research SA
The dislocation densities during the quench of a 0.215wt.%C steel in martensite and in austenite are investigated by a HEXRD in situ experiment on a synchrotron beamline. The experiment configuration offers an excellent time resolution well adapted to the investigation of martensitic transformation kinetics. The dislocation densities in both phases increase as the transformation proceeds. The dislocations densities in martensite are certainly heterogeneously distributed in between the laths according to some recent post-mortem observations. These distributions support the views assuming that lath martensite behaves as a “multiphase” aggregate. In austenite, high dislocation densities are reported at the end of martensitic transformation meaning that residual austenite is also a hard phase.
9:30 AM
Effect of Phase Stability of Retained Austenite during Deformation in Low-alloy Multiphase Steels: Avala Lavakumar1; Myeong-heom PARK1; Hiroki Adachi2; Masugu Sato3; Nobuhiro Tsuji1; 1Kyoto University; 2University of Hyogo; 3Japan Synchrotron Radiation Research Institute (JARSI), Sayo-gun, Hyogo
Transformation induced plasticity (TRIP) effect is one of the most prominent ways to enhance mechanical properties in lean compositional steel, with aid of retained austenite(R.A). The performance of retained austenite mostly depends on its carbon concentration, size, shape, and neighboring phases. However, there is no systematic study dedicated to understanding the effect of neighboring phases on the stability of R.A. The objective of the present study is to clarify the role of neighboring phases on the transformation of R.A during room-temperature deformation. In this study, two kinds of multiphase microstructures were developed, one with ferrite and R.A, and another with ferrite, R.A, and martensite. It was found that the R.A surrounded only by ferrite was transformed at a much faster rate than the R.A surrounded by ferrite and martensite. To explore the reason for the stability of R.A, stress partitioning among the phases was investigated by synchrotron-based in-situ tensile test.
9:50 AM
Microstructural and Plastic Deformation Study of a Multi-phase Advanced High Strength Steel: Afm Monowar Hossain1; Nilesh Kumar; 1University of Alabama Tuscaloosa
Multi-phase (MP) steels fall under the category of advanced high strength steel (AHSS) that are increasingly being used for light-weighting of automotive vehicles. By changing processing parameters, number of phases and their fractions can be controlled, thereby controlling mechanical properties of MP steels. To investigate processing - microstructure – mechanical property correlation of a MP steel, thermo-mechanical processing (TMP) was performed using Gleeble® - a TMP simulator. It was followed by microstructural analysis and mechanical testing using advanced characterization tools including digital image correlation (DIC) and in-situ SEM tensile tester. Electron backscatter diffraction (EBSD) was used before and after plastic deformation to understand crystallography of plastic deformation. The elastic behavior, strength, and ductility were determined and compared with the alloy in different processing conditions. A detailed analysis of the DIC, in-situ tensile test data, and EBSD is in-progress and will be discussed in this presentation.
10:10 AM
Strain Rate Sensitive Martensite Transformation in a Q&P Steel: Christopher Finfrock1; Melissa Thrun1; Trevor Ballard1; John Copley1; Benjamin Ellyson1; Amy Clarke1; Kester Clarke1; 1Colorado School of Mines
Quenching and partitioning (Q&P) steels use the deformation-induced transformation of austenite to martensite (DIMT) to enhance formability and crash performance by increasing the work hardening rate. However, strain state, strain rate, and workpiece temperature can influence DIMT and thus influence the mechanical performance. Competing mechanisms control DIMT across a spectrum of strain rates: at intermediate strain rates (0.1 1/s) , DIMT is restricted by adiabatic heat accumulation and corresponding stabilization of austenite; at dynamic rates (1000 1/s), shear bands (the primary sites for martensite nucleation) form more rapidly and thus accelerate DIMT. This presentation will explore the strain rate sensitivity of DIMT with interrupted formability tests and Hopkinson bar tensile tests with in-situ synchrotron diffraction analysis, along with complementary characterization.