Use of Large Scale Facilities to Understand the Physical Metallurgy of Fe-based Alloys: Session II
Program Organizers: Sebastien Allain, Institut Jean Lamour; Alexis Deschamps, Genoble Institute of Technology; MingXin Huang, University of Hong Kong; Amy Clarke, Los Alamos National Laboratory; C. Tasan, Massachusetts Institute of Technology
Monday 2:30 PM
February 24, 2020
Room: Mission Hills
Location: Marriott Marquis Hotel
Session Chair: Hung-Wei Yen, National Taiwan University; Alexis Deschamps, SIMAP
2:30 PM
Carbide-free Bainite Transformations in Non-isothermal Conditions Investigated
by In-situ High-energy X-ray Diffraction Experiments: Cecile Rampelberg1; Guillaume Geandier1; Julien Teixeira1; Thomas Sourmail2; Sébastien Allain1; 1Institut Jean Lamour; 2Ascometal
Carbide-Free Bainite (CFB) transformation has been investigated in situ on three industrial grades by High Energy X-Ray Diffraction. These experiments has been realized on P07 beamline in PETRA III at DESY (Hamburg) with a monochromatic beam (100keV). High flux from synchrotron source and high-throughput 2D detector (Perkin-Elmer) allows the collection of Debye-Scherrer diffraction patterns at high rate (10 Hz). Three bainitizing thermal schedules have been studied : conventionnel isothermal holdings, continuous cooling (close to industrial condition after forging) and multi-step cooling sequences (successive isothermal steps with decreasing temperatures to approximate a continuous cooling and decompose transformation sequences). Coupled with direct post mortem microstructural observations and mechanical tests, these analysis provide a better understanding of phase transformation mechanisms and kinetics during CFB formation.
2:50 PM
Carbon Heterogeneities in Austenite during Quenching & Partitioning (Q&P) Process Revealed by In Situ High Energy X-ray Diffraction (HEXRD) Experiments: Guillaume Geandier1; Sebastien Allain1; Steve Gaudez1; Frederic Danoix2; Michel Soler3; Mohamed Goune4; 1Institut Jean Lamour; 2Normandie Université , UNIROUEN, INSA Rouen, CNRS; 3Maizières Automotive Products, Arcelormittal Maizières Research SA; 4Institut de Chimie de la Matière Condensée de Bordeaux
Based on the evolution of the positions and intensities of the diffraction peaks, high energy X-ray diffraction (HEXRD) is recognized as the ultimate method to follow quantitatively in situ phase transformations in steels. However, the possible asymmetricity of diffraction peaks is seldom considered, and is here shown to bear information. A procedure for quantifying their skewness is proposed. In the case of a model third generation high strength steels obtained by quench and partitioning (Q&P), the skewness is shown to be due to carbon heterogeneities at austenite/martensite interfaces, in agreement with prior post mortem atom probe tomography (APT) investigations.
3:10 PM
Real-time Investigation of Recovery, Recrystallization and Austenite Transformation during Annealing of a Cold-rolled Steel Using High Energy X-ray Diffraction (HEXRD): Marc Moreno1; Guillaume Geandier1; Julien Teixeira1; Jean-Christophe Hell2; Frédéric Bonnet2; Sebastien Allain1; 1Institut Jean Lamour; 2ArcelorMittal Maizières Research SA
We propose a new method based on High Energy X-Ray Diffraction (HEXRD) on synchrotron beamline to follow in situ during a single experiment the recovery, the recrystallization and the austenite transformation when annealing a cold-rolled ferritic steel. Phase transformations and recovery kinetics are determined on the basis of a conventional Rietveld refinement procedure coupled with a Williamson-Hall approach. The study of the recrystallization has required on the contrary the development of a new procedure inspired by the 3D X-ray diffraction tomography. It is based on a systematic detection of individual diffraction spots related to newly recrystallized grains appearing on Debye-Scherrer rings. The method has been applied to the case of ferrite/pearlite steels annealed to manufacture Dual-Phase steels. Powder diffraction experiments in transmission (100 keV) have been conducted at DESY–P07. Diffraction patterns have been acquired all along the annealing treatment. Deduced kinetics is validated by more conventional ex situ methods.
3:30 PM
In-situ Synchrotron X-ray Diffraction Stress Analysis during Laser Surface Line Hardening of Samples with Specific Geometric Features: Dominik Kiefer1; Jens Gibmeier1; Fabian Wilde2; Felix Beckmann2; 1Karlsruhe Institute of Technology - Institute for Applied Materials; 2Helmholtz-Zentrum Geesthacht - Institute of Materials Research
Recently, a synchrotron X-ray diffraction based measuring strategy was established for real time monitoring of local stress development and phase transformations during laser surface hardening of steel samples. Here, we report about AISI 4140 steel samples that were line hardened using a 4 kW high power diode laser while controlling the maximum surface temperature. In-situ X-ray diffraction analyses during temperature controlled laser hardening experiments were carried out at the synchrotron beamline P05@PETRAIII at DESY in Hamburg using a photon energy of 10.9 keV. Local phase transformation kinetics and stress evolution at the sample surface were monitored at a rate of 50 Hz with a spatial resolution of <Ø1 mm. To quantify sample geometry effects on the stress formation and hence the residual stress state in the process zone, samples with specific geometric features (surface curvatures with defined radii and bridged structures) were investigated and compared with results of flat specimen.
3:50 PM
In situ HEXRD Determination and Numerical Simulation of Internal Stresses during HeatTtreatment of Carburized and Carbonitrided Low-alloyed Steels: Karthikeyan Jeyabalan1; Julien Teixeira1; Sabine Denis1; Guillaume Geandier1; Jacky Dulcy1; Benoît Denand1; Grégory Michel2; Simon Catteau3; Marc Courteaux4; 1Institute Jean Lamour; 2IRT-M2P; 3Ascometal - CREAS; 4Groupe PSA - Centre Technique de Belchamp
Thermochemical treatments like carburizing and carbonitriding allow to improve the combinations of properties in low-alloyed steels, which depend mainly on the distributions of residual stresses and microstructures. This contribution presents a full experimental and simulation analysis of the microstructural evolutions highlighting the influence of nitrogen, and of the internal stresses evolutions during such treatments. High Energy X-Ray Diffraction (HEXRD) is employed to track in situ, during cooling, the internal stresses evolutions and the austenite decomposition kinetics, throughout the carbon and nitrogen-enriched case. A coupled thermal, metallurgical and mechanical model predicting the phase transformation kinetics and the stress evolutions during cooling is assessed on the basis of these in situ experiments combined with post mortem microstructure observations. For carburizing, classical analysis regarding stresses evolutions is confirmed by the in situ characterization. For carbonitriding, unexpected evolutions occur, which are interpreted on the basis of the experiments and the simulation.
4:10 PM Break
4:30 PM
Stress Tensor Determination during Phase Transformation of a Metal Matrix Composite using In situ High Energy X-ray Diffraction: Guillaume Geandier1; Lilian Vautrot1; Benoît Denand1; Sabine Denis1; 1Intitut Jean Lamour
In situ high energy X-ray diffraction using a synchrotron source performed on a steel metal matrix composite reinforced by TiC allows following the evolutions during cooling of the phase fractions and the mean cell parameters (Rietveld analysis). Using a radiation furnace with a controlled rotation of the specimen, the evolutions during cooling of the components of the stress tensor in the composite can be obtained. Thus, it has been shown that the matrix and the reinforcements are under a hydrostatic stress state all along cooling even during the phase transformation. Using the stress free cell parameters and their evolutions with temperature, it comes out that from 900°C to the martensitic transformation, the compressive stresses increase in the reinforcements and small compressive stresses exist in the austenite. As the transformation occurs the stresses relax largely in the reinforcements, the compressive stresses increase in the austenite and the martensite undergoes tensile stresses.
4:50 PM
Microstructure Evolution and Phase Transformations during Deformation of Metastable Austenitic CrMnNi Steel as Revealed by In situ Synchrotron Radiation X-ray Diffraction: Christiane Ullrich1; Stefan Martin1; Christian Schimpf1; Andreas Stark2; Norbert Schell2; David Rafaja1; 1TU Bergakademie Freiberg; 2Helmholtz-Zentrum Geesthacht
In situ X-ray diffraction experiments using synchrotron radiation were performed during uniaxial compression at varying temperatures in order to explore the deformation mechanisms occurring in an austenitic 16Cr-7Mn-3Ni TRIP/TWIP steel. The 2D diffraction data collected in transmission geometry revealed the phase composition, residual lattice stress, microstrain caused by dislocations, stacking fault probability and preferred orientation of crystallites in individual deformation steps. These microstructure characteristics were utilized to describe the microstructure evolution of the TRIP/TWIP steel during the plastic deformation. The main deformation mechanisms, which are the formation of dislocations and stacking faults in austenite, and the transformation of austenite to epsilon- and alpha´-martensites, were quantified as functions of the external load and temperature. Based on these results, a model describing the contributions of individual deformation mechanisms to the plastic deformation of the steel as a function of the temperature-dependent stacking fault energy was formulated.
5:10 PM
In situ Quantitative Study of Retained Austenite Mechanical Stability in 3rd Generation TRIP-aided Steels by High-Energy X-ray Diffraction on Synchrotron Beamline: Mathias Lamari1; Sebastien Allain1; Guillaume Geandier1; Julien Teixeira1; Astrid Perlade2; Kangying Zhu2; 1Institut Jean Lamour; 2ArcelorMittal Maizières Research SA, Product Center
The evolution of austenite stability in medium manganese steels during manufacturing and further mechanical loading has been investigated by in situ High Energy X-Ray Diffraction. The presented experiments have been realized on Petra-III P07 line at Desy (Hamburg). The high energy (100 keV) coupled with a high-performance detector (Perkin-Elmer) enable high acquisition rates and thus in situ time-resolved investigations. Two microstructures with different morphology (globular and fibrous) produced by intercritical annealing exploiting the Austenite Reversed Transformation (ART) mechanism have been studied and their formation explained by analyzing the solute partitioning between austenite and ferrite during the thermal treatment. Tensile tests have been then conducted on the two steels at different rates to quantify the mechanically induced martensitic transformations and determine the local stresses in the constituting phases of the steels.
5:30 PM Cancelled
Combining Interrupted Hopkinson Bar Tensile Tests with Synchrotron XRD to Study Work Hardening Behavior of Q&P Steels at High Strain Rates: Ming Wang1; MingXin Huang1; 1University of Hong Kong
Quenching and partitioning (Q&P) steel is a promising material for automotive application. It possesses high strength and good ductility due to deformation induced martensitic transformation. The present work investigated the deformation behavior of QP980 and QP1400 steels at different strain rates (0.001 s-1 to 1000 s-1). The corresponding stress-strain curves at 1000 s-1 indicate that the work hardening rate of QP1400 steel during plastic deformation reaches a minimum before a maximum, which is different from that of QP980 steel showing a continuous decrease. To study this unexpected phenomenon, specimens subjected to different strain levels at 1000 s-1 were obtained by interrupted tensile tests using a recovery Hopkinson bar technique. The evolution of austenite fraction and dislocation density was quantified by synchrotron X-ray diffraction. The results reveal that the occurrence of massive martensitic transformation in a specific strain range can assist plastic deformation and subsequently lower the work hardening rate.