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The surface and subsurface conditions of components are critical for their functional properties. Every manufacturing process modifies the surface condition as a consequence of its mechanical, chemical, and thermal impact or combinations of the three. The depth of the affected zone varies for different machining operations and is related to the process parameters and characteristics. Furthermore, the initial material state has a decisive influence on the modifications that lead to the final surface conditions. With this knowledge, the collaborative research center CRC/Transregio 136 “Process Signatures” started a first joint investigation to analyze the influence of several machining operations on the surface modifications of uniformly premanufactured samples in a broad study. The present paper focusses on four defined process chains which were analyzed in detail regarding the resulting surface conditions as a function of the initial state. Two different workpiece geometries of the same initial material (AISI 4140, 42CrMo4 (1.7225) classified according to DIN EN ISO 683-2) were treated in two different heat treating lines. Samples annealed to a ferritic-perlitic microstructure were additionally deep rolled as starting condition. Quenched and tempered samples were induction hardened before further process application. These two states were then submitted to six different manufacturing processes, i.e., grinding (with mainly mechanical or thermal impact), precision turning (mainly mechanical), laser processing (mainly thermal), electrical discharge machining (EDM, mainly thermal) and electrochemical machining (ECM, (mainly chemical impact). The resulting surface conditions were investigated after each step of the manufacturing chain by specialized analysis techniques regarding residual stresses, microstructure, and hardness distribution. Based on the process knowledge and on the systematic characterizations, the characteristics and depths of the material modifications, as well as their underlying mechanisms and causes, were investigated. Mechanisms occurring within AISI 4140 steel (42CrMo4) due to thermal, mechanical or mixed impacts were identified as work hardening, stress relief, recrystallization, re-hardening and melting, grain growth, and rearrangement of dislocations.
Florian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals 2021, 11, 1102 .
AMA StyleFlorian Borchers, Brigitte Clausen, Lisa Ehle, Marco Eich, Jérémy Epp, Friedhelm Frerichs, Matthias Hettig, Andreas Klink, Ewald Kohls, Yang Lu, Heiner Meyer, Bob Rommes, Sebastian Schneider, Rebecca Strunk, Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals. 2021; 11 (7):1102.
Chicago/Turabian StyleFlorian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. 2021. "The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes." Metals 11, no. 7: 1102.
In this work, the microstructural evolution during the dynamic transformation of austenite to bainite was directly observed by in-situ high energy synchrotron X-ray diffraction measurements during warm uniaxial compression performed at the P07 beamline of PETRA III, DESY (Deutsches Elektronen-Synchrotron). Plastic deformation triggers the phase transformation, which is continuously stimulated by the introduction of dynamic dislocations into the austenite. This scenario accelerates the kinetics of bainite formation in comparison with conventional isothermal treatment. No mechanical stabilization of austenite was observed during dynamic transformation. Evidence of carbon partitioning between phases during plastic deformation was obtained. Further post-process investigations suggest that the bainitic microstructure developed during compression is oriented perpendicular to the loading direction. The findings open up new possibilities to design carbide-free bainitic microstructures directly via thermomechanical processing.
William Bevilaqua; Jérémy Epp; Heiner Meyer; Juan Dong; Hans Roelofs; Alexandre Da Silva Rocha; Afonso Reguly. Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction. Metals 2021, 11, 467 .
AMA StyleWilliam Bevilaqua, Jérémy Epp, Heiner Meyer, Juan Dong, Hans Roelofs, Alexandre Da Silva Rocha, Afonso Reguly. Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction. Metals. 2021; 11 (3):467.
Chicago/Turabian StyleWilliam Bevilaqua; Jérémy Epp; Heiner Meyer; Juan Dong; Hans Roelofs; Alexandre Da Silva Rocha; Afonso Reguly. 2021. "Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction." Metals 11, no. 3: 467.
The surface and subsurface conditions of components are significant for their functional properties. Every manufacturing process step changes the surface condition due to its mechanical, chemical and/or thermal impact. The depth of the affected zone varies for different machining operations, and is predetermined by the process parameters and characteristics. Furthermore, the initial state has a decisive influence on the interactions that lead to the final surface conditions. The aim of the investigation presented here is to compare the influence of the load characteristics over the depth applied to manufactured components by several different machining operations and to determine the causing mechanisms. In order to ensure better comparability between the surface modifications caused by different machining operations, the same material was used (AISI 4140; German steel grade 42CrMo4 acc. to DIN EN 10083-3) and annealed to a ferritic-pearlitic microstructure. Based on interdisciplinary cooperation within the collaborative research center CRC/Transregio 136 “Process Signatures”, seven different manufacturing processes, i.e., grinding, turning, deep rolling, laser processing, inductive heat treatment, electrical discharge machining (EDM) and electrochemical machining (ECM), were used, and the resulting surface zones were investigated by highly specialized analysis techniques. This work presents the results of X-ray measurements, hardness measurements and electron microscopic investigations. As a result, the characteristics and depths of the material modifications, as well as their underlying mechanisms and causes, were studied. Mechanisms occurring within 42CrMo4 steel due to thermal, mechanical, chemical or mixed impacts were identified as phase transformation, solidification and strengthening due to dislocation generation and accumulation, continuum dynamic recrystallization and dynamic recovery, as well as chemical reactions.
Florian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals 2020, 10, 895 .
AMA StyleFlorian Borchers, Brigitte Clausen, Sandro Eckert, Lisa Ehle, Jeremy Epp, Simon Harst, Matthias Hettig, Andreas Klink, Ewald Kohls, Heiner Meyer, Markus Meurer, Bob Rommes, Sebastian Schneider, Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals. 2020; 10 (7):895.
Chicago/Turabian StyleFlorian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. 2020. "Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth." Metals 10, no. 7: 895.
In this study, cylindrical grinding of a 42CrMo4 (AISI 4140) steel with varied grinding sequence stages is analyzed regarding the effect of the different loads during multistage grinding up to the resulting final residual stress state and material structure. The grinding process was adjusted in a way to enhance the mechanical load with varying intensity and generate a pronounced compressive residual stress state in the final grinding step. Furthermore, consecutive multistage grinding processes were carried out and investigated. Using a mobile XRD system with a cos α method mounted on a robotic positioning arm, repetitive measurements of the ground surfaces were performed in the machine tool without sample removal, giving information about the surface residual stress development for each step of the process sequence. The information about the surface integrity development and possible effects of the grinding process during each step is relevant for the contact conditions and modification mechanisms which lead to the final surface integrity. It is shown that the final material state, normally accessible in post-process investigations, can also be achieved reliably by sequencing the process into several steps of a regular grinding process and depends strongly on the contact parameters in a non-linear way. It could be shown, that even the spark out step can lead to significant changes in the surface residual stress state.
Florian Borchers; Heiner Meyer; Carsten Heinzel; Daniel Meyer; Jérémy Epp. Development of surface residual stress and surface state of 42CrMo4 in multistage grinding. Procedia CIRP 2020, 87, 198 -203.
AMA StyleFlorian Borchers, Heiner Meyer, Carsten Heinzel, Daniel Meyer, Jérémy Epp. Development of surface residual stress and surface state of 42CrMo4 in multistage grinding. Procedia CIRP. 2020; 87 ():198-203.
Chicago/Turabian StyleFlorian Borchers; Heiner Meyer; Carsten Heinzel; Daniel Meyer; Jérémy Epp. 2020. "Development of surface residual stress and surface state of 42CrMo4 in multistage grinding." Procedia CIRP 87, no. : 198-203.
The effects of hot deformation on the bainitic transformation of a low carbon steel during continuous cooling were comprehensively studied through in situ high-energy synchrotron X-ray diffraction, dilatometry, and ex situ microstructural characterizations. The obtained results indicated that the prior deformation of austenite at 950 °C accelerates the bainite formation at the early stages. During the ongoing of the transformation, both the overall kinetics of bainite and carbon enrichment of austenite are lower in deformed austenite. The bainitic microstructure developed from deformed austenite is more refined and presents the same retained austenite content at room temperature with slightly lower carbon content when compared with the undeformed sample. Besides, a significant higher dilatation strain was measured during the bainitic transformation in the deformed sample, which can be explained by the crystallographic texture in hot deformed austenite. The evolution of the peak broadening of the {220}γ and {211}α reflections during bainitic transformation are discussed in detail.
William Lemos Bevilaqua; Jérémy Epp; Heiner Meyer; Alexandre Da Silva Rocha; Hans Roelofs. In Situ Investigation of the Bainitic Transformation from Deformed Austenite During Continuous Cooling in a Low Carbon Mn-Si-Cr-Mo Steel. Metallurgical and Materials Transactions A 2020, 51, 3627 -3637.
AMA StyleWilliam Lemos Bevilaqua, Jérémy Epp, Heiner Meyer, Alexandre Da Silva Rocha, Hans Roelofs. In Situ Investigation of the Bainitic Transformation from Deformed Austenite During Continuous Cooling in a Low Carbon Mn-Si-Cr-Mo Steel. Metallurgical and Materials Transactions A. 2020; 51 (7):3627-3637.
Chicago/Turabian StyleWilliam Lemos Bevilaqua; Jérémy Epp; Heiner Meyer; Alexandre Da Silva Rocha; Hans Roelofs. 2020. "In Situ Investigation of the Bainitic Transformation from Deformed Austenite During Continuous Cooling in a Low Carbon Mn-Si-Cr-Mo Steel." Metallurgical and Materials Transactions A 51, no. 7: 3627-3637.
Jeremy Epp; Juan Dong; Heiner Meyer; Annika Bohlen. Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments. Scripta Materialia 2020, 177, 27 -31.
AMA StyleJeremy Epp, Juan Dong, Heiner Meyer, Annika Bohlen. Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments. Scripta Materialia. 2020; 177 ():27-31.
Chicago/Turabian StyleJeremy Epp; Juan Dong; Heiner Meyer; Annika Bohlen. 2020. "Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments." Scripta Materialia 177, no. : 27-31.
Mechanical loading scenarios, comparable to a deep rolling process, were reproduced in static indentation experiments on AISI 4140H steel samples with a cylindrical deep rolling tool and investigated in situ with synchrotron radiation at the European Synchrotron Radiation Facility (ESRF) on beamline ID11. Through the use of spatially resolved diffraction data, two-dimensional (2D) equivalent von Mises stress maps were recorded during loading and after unloading. The material modifications were analyzed in the material below the contact zone for different loading conditions. It was demonstrated that the characteristics of internal material load and residual stress distributions can be evaluated through data fitting and the effect of the applied force could be linked to the stress fields by an empirical model. The experimental values were then compared to a contact mechanics approach in order to analyze the correlation between the theoretical maximum loading stresses and the stored elastic residual stresses remaining by considering the dissipation of a certain amount of energy through plastic deformation.
Heiner Meyer; Jérémy Epp. Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling. Quantum Beam Science 2020, 4, 3 .
AMA StyleHeiner Meyer, Jérémy Epp. Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling. Quantum Beam Science. 2020; 4 (1):3.
Chicago/Turabian StyleHeiner Meyer; Jérémy Epp. 2020. "Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling." Quantum Beam Science 4, no. 1: 3.
Residual stresses originating from elasto-plastic deformation during mechanical processing can be analyzed post-process with various known methods. A new measurement method to measure and evaluate the strain and stress fields in situ under the contact point during a deep rolling process was developed to describe the dependence of the residual stresses from the internal material load. Using synchrotron radiation at European Synchrotron Radiation Facility (ESRF) (ID11), diffraction measurements were performed in transmission geometry during dynamical loading with different process parameters. The strain and stress fields were analyzed with high spatial resolution in an 8 mm × 4 mm area around the contact point during the process using a 13-mm tungsten carbide roller on samples of AISI 4140H steel. Fast data acquisition allowed the reconstruction of full two-dimensional (2D) strain and stress maps. These could be used to determine the response from the initial material state in front of the roller to the mechanically loaded region with plastic deformation up to the processed material with the resulting residual stresses. This comprehensive analysis was then used to link the internal material load with the resulting residual stresses in the final material state.
Heiner Meyer; Jérémy Epp. In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel. Quantum Beam Science 2018, 2, 20 .
AMA StyleHeiner Meyer, Jérémy Epp. In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel. Quantum Beam Science. 2018; 2 (4):20.
Chicago/Turabian StyleHeiner Meyer; Jérémy Epp. 2018. "In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel." Quantum Beam Science 2, no. 4: 20.
A deep rolling process was applied on 4140H steel specimens with a self-built loading frame and investigated in situ with neutron radiation using the SALSA instrument at the Institut Laue-Langevin (ILL). A neutron diffraction stress imaging approach was developed and used to determine material changes from the surface up to several millimeters inside the material by single expositions. The strains could be evaluated as deviations of the diffraction signal along the height of an area detector, and the theoretical maximum depth resolution was given by geometrical magnification together with the detector pixel size. The results of these experiments together with complementary post-process investigations could be used to link the internal load during the process with resulting material modifications such as the generated residual strains.
Heiner Meyer; Jérémy Epp; Thilo Pirling; Hans-Werner Zoch. In Situ Investigations of Elastic Strain State in Deep Rolled 4140H Steel by Neutron Diffraction Method. Materials Performance and Characterization 2018, 7, 1 .
AMA StyleHeiner Meyer, Jérémy Epp, Thilo Pirling, Hans-Werner Zoch. In Situ Investigations of Elastic Strain State in Deep Rolled 4140H Steel by Neutron Diffraction Method. Materials Performance and Characterization. 2018; 7 (4):1.
Chicago/Turabian StyleHeiner Meyer; Jérémy Epp; Thilo Pirling; Hans-Werner Zoch. 2018. "In Situ Investigations of Elastic Strain State in Deep Rolled 4140H Steel by Neutron Diffraction Method." Materials Performance and Characterization 7, no. 4: 1.
The newly proposed concept of Process Signatures enables the comparison of seemingly different manufacturing processes via a process-independent approach based on the analysis of the loading condition and resulting material modification. This contribution compares the recently published results, based on numerically achieved data for the development of Process Signatures for sole surface and volume heatings without phase transformations, with the experimental data. The numerical approach applies the moving heat source theory in combination with energetic quantities. The external thermal loadings of both processes were characterized by the resulting temperature development, which correlates with a change in the residual stress state. The numerical investigations show that surface and volume heatings are interchangeable for certain parameter regimes regarding the changes in the residual stress state. Mainly, temperature gradients and thermal diffusion are responsible for the considered modifications. The applied surface- and volume-heating models are used in shallow cut grinding and induction heating, respectively. The comparison of numerical and experimental data reveals similarities, but also some systematic deviations of the residual stresses at the surface. The evaluation and final discussion support the assertion for very fast stress relaxation processes within the subsurface region. A consequence would be that the stress relaxation processes, which are not yet included in the numerical models, must be included in the Process Signatures for sole thermal impacts.
Friedhelm Frerichs; Heiner Meyer; Rebecca Strunk; Benjamin Kolkwitz; Jeremy Epp. Development of a Process Signature for Manufacturing Processes with Thermal Loads. Metallurgical and Materials Transactions A 2018, 49, 3419 -3429.
AMA StyleFriedhelm Frerichs, Heiner Meyer, Rebecca Strunk, Benjamin Kolkwitz, Jeremy Epp. Development of a Process Signature for Manufacturing Processes with Thermal Loads. Metallurgical and Materials Transactions A. 2018; 49 (8):3419-3429.
Chicago/Turabian StyleFriedhelm Frerichs; Heiner Meyer; Rebecca Strunk; Benjamin Kolkwitz; Jeremy Epp. 2018. "Development of a Process Signature for Manufacturing Processes with Thermal Loads." Metallurgical and Materials Transactions A 49, no. 8: 3419-3429.
Heiner Meyer; Jérémy Epp; Hans-Werner Zoch. Residual stress and dislocation density development in single track deep rolled AISI 4140H steel. Procedia CIRP 2018, 71, 192 -197.
AMA StyleHeiner Meyer, Jérémy Epp, Hans-Werner Zoch. Residual stress and dislocation density development in single track deep rolled AISI 4140H steel. Procedia CIRP. 2018; 71 ():192-197.
Chicago/Turabian StyleHeiner Meyer; Jérémy Epp; Hans-Werner Zoch. 2018. "Residual stress and dislocation density development in single track deep rolled AISI 4140H steel." Procedia CIRP 71, no. : 192-197.
J. Epp; H.-W. Zoch; Heiner Meyer. In situ X-Ray Diffraction Investigation of Surface Modifications in a Deep Rolling Process under Static Condition. Residual Stresses 2016 2016, 2, 431 -436.
AMA StyleJ. Epp, H.-W. Zoch, Heiner Meyer. In situ X-Ray Diffraction Investigation of Surface Modifications in a Deep Rolling Process under Static Condition. Residual Stresses 2016. 2016; 2 ():431-436.
Chicago/Turabian StyleJ. Epp; H.-W. Zoch; Heiner Meyer. 2016. "In situ X-Ray Diffraction Investigation of Surface Modifications in a Deep Rolling Process under Static Condition." Residual Stresses 2016 2, no. : 431-436.