Search results for: Ernst Kozeschnik

Items from 1 to 20 out of 37 results

article

Advanced Thermo-mechanical Process for Homogenous Hierarchical Microstructures in HSLA Steels

Carina Ledermueller, Ernst Kozeschnik, Richard F. Webster, Sophie Primig

Metallurgical and Materials Transactions A > 2019 > 50 > 12 > 5800-5815

Engineering microstructures in high-strength low-alloy steels via advanced thermo-mechanical processing is a promising approach to overcome challenges around low work hardenability and toughness in ultrafine-grained mild steels. Recently, multiscale-hierarchical microstructures with ultrafine grains and two populations of precipitates decorating high-angle grain boundaries and dislocation structures...

article

Temperature-dependent strain hardening, precipitation and deformation-induced microstructure evolution in AA 6061

Johannes Kreyca, Ernst Kozeschnik

Materials Science and Engineering: A > 2017 > 708 > C > 411-418

The effect of β′′ precipitation on strain hardening and yield stress evolution in an A6061 aluminium alloy is studied experimentally and through thermokinetic computer simulation. Samples were deformed by compression at temperatures from 25 to 500°C to strains of about 0.4 and three different precipitation states. Simulations on the thermal stability of β′′ are conducted on an equivalent model Al-Mg-Si...

article

Phase evolution and carbon redistribution during continuous tempering of martensite studied with high resolution techniques

Annika Vieweg, Erwin Povoden-Karadeniz, Gerald Ressel, Petri Prevedel, more

Materials & Design > 2017 > 136 > C > 214-222

Using high resolution techniques, such as, 3D atom probe tomography, transmission electron microscopy and synchrotron radiation, the continuous tempering process of a 50CrMo4 steel is analyzed. Differences of continuous heating compared to isothermal holding at certain tempering temperatures are discussed. Focus is laid on in-depth characterization of phase development and carbon redistribution effects,...

article

Analysis of the Temperature and Strain-Rate Dependences of Strain Hardening

Johannes Kreyca, Ernst Kozeschnik

Metallurgical and Materials Transactions A > 2018 > 49 > 1 > 18-21

A classical constitutive modeling-based Ansatz for the impact of thermal activation on the stress–strain response of metallic materials is compared with the state parameter-based Kocks–Mecking model. The predicted functional dependencies suggest that, in the first approach, only the dislocation storage mechanism is a thermally activated process, whereas, in the second approach, only the mechanism...

article

Carbide Precipitation in 2.25 Cr-1 Mo Bainitic Steel: Effect of Heating and Isothermal Tempering Conditions

Sylvain Dépinoy, Caroline Toffolon-Masclet, Stéphane Urvoy, Justine Roubaud, more

Metallurgical and Materials Transactions A > 2017 > 48 > 5 > 2164-2178

The effect of the tempering heat treatment, including heating prior to the isothermal step, on carbide precipitation has been determined in a 2.25 Cr-1 Mo bainitic steel for thick-walled applications. The carbides were identified using their amount of metallic elements, morphology, nucleation sites, and diffraction patterns. The evolution of carbide phase fraction, morphology, and composition was...

article

The Cr-Nb-Si system: Improved thermodynamic modelling and its use in simulation of Laves phase in steel

Aurélie Jacob, Erwin Povoden-Karadeniz, Ernst Kozeschnik

Calphad > 2017 > 56 > C > 80-91

Thermodynamic modelling of the Cr-Nb-Si ternary system is revised considering new findings in the binary Cr-Nb and extension to multicomponent systems. Thermodynamic model parameters of intermetallic phases are re-optimized based on density functional theory (DFT) calculations and experimental data. Particular attention was given to the transformations of Laves phase polytypes (i.e. C14 and C15)....

article

Dissolution of hardening phases during deformation in an A6061 Aluminium alloy

Johannes Kreyca, Ernst Kozeschnik

Procedia Engineering > 2017 > 207 > C > 37-41

The temperature limit for the technological usage of an A6061 aluminium alloy is investigated taking into account the initial precipitation state and the stability of hardening phases during the deformation process. In a critical temperature range, the dissolution of precipitates occurs parallel to deformation processes resulting in a characteristic strain rate-dependent shape of the stress strain...

article

Modelling hydrogen migration and trapping in steels

Miles Alexander Stopher, Peter Lang, Ernst Kozeschnik, Pedro E.J. Rivera-Diaz-del-Castillo

Materials & Design > 2016 > 106 > C > 205-215

Hydrogen embrittlement remains of critical concern in the design of strong and reliable microstructures in steels. The role of microstructure in susceptibility to hydrogen trapping is evaluated using a numerical thermokinetic simulation approach. The simulation scheme is applied to evaluate variations in dislocation density and grain size in pure ferritic iron, ferritic and martensitic low alloy steels...

article

CALPHAD-based alloy design for advanced automotive steels – Part II: Compositional and microstructural modification for advanced carburizing steels

Sung Chul Cha, Seung-Hyun Hong, Myung-Yeon Kim, Jihye Park, more

Calphad > 2016 > 54 > C > 172-180

The CALPHAD-based computational techniques established in the first part of this series [1] have been applied for the development of advanced carburizing steels used for gears in vehicle transmissions. To improve the strength and hardenability of a conventional carburizing steel, the alloying composition has been modified based on the calculation of phase equilibria and the prediction of mechanical...

article

A Model for Static Recrystallization with Simultaneous Precipitation and Solute Drag

Heinrich Buken, Ernst Kozeschnik

Metallurgical and Materials Transactions A > 2017 > 48 > 6 > 2812-2818

In the present work, we introduce a state parameter-based microstructure evolution model, which incorporates the effect of solute atoms and precipitates on recrystallization kinetics. The model accounts for local precipitate coarsening at grain boundaries, which promotes an average grain boundary movement even if the Zener pinning force exceeds the driving force for recrystallization. The impact of...

article

[O16] Thermodynamics of the Pd-Mn system and phase stability of L10-based Pd1-xMn1-yFex+y

Erwin Povoden-Karadeniz, Frank Moszner, Stefan Pogatscher, Peter J. Uggowitzer, more

Calphad > 2015 > 51 > C > 350

article

[P90] Thermodynamics of carbon trapping at dislocations in martensite

Yao V Shan, Walter Mayer, Ernst Kozeschnik

Calphad > 2015 > 51 > C > 402

article

Modeling precipitation thermodynamics and kinetics in type 316 austenitic stainless steels with varying composition as an initial step toward predicting phase stability during irradiation

Jae-Hyeok Shim, Erwin Povoden-Karadeniz, Ernst Kozeschnik, Brian D. Wirth

Journal of Nuclear Materials > 2015 > 462 > C > 250-257

The long-term evolution of precipitates in type 316 austenitic stainless steels at 400°C has been simulated using a numerical model based on classical nucleation theory and the thermodynamic extremum principle. Particular attention has been paid to the precipitation of radiation-induced phases such as γ′ and G phases. In addition to the original compositions, the compositions for radiation-induced...

article

Modelling the influence of austenitisation temperature on hydrogen trapping in Nb containing martensitic steels

Peter Lang, Markus Rath, Ernst Kozeschnik, Pedro E.J. Rivera-Diaz-del-Castillo

Scripta Materialia > 2015 > 101 > C > 60-63

Hydrogen trapping behaviour is investigated by means of thermokinetic simulations in a martensitic steel. The heat treatment consists of austenitisation followed by quenching and tempering. The model prescribes a minimum in hydrogen trapping at an austenitisation temperature of 1050°C. Below this temperature, austenite grain boundaries are the prevailing trap, whereas niobium atoms in solid solution...

article

Simulation of the effect of composition on the precipitation in 6xxx Al alloys during continuous-heating DSC

Peter Lang, Erwin Povoden-Karadeniz, Ahmad Falahati, Ernst Kozeschnik

Journal of Alloys and Compounds > 2014 > 612 > Complete > 443-449

The precipitation behaviour of Al–Mg–Si alloys has been studied by differential scanning calorimetry (DSC) and by thermo-kinetic modelling. Three industrial alloys with different main solute contents, namely Mg, Si, Cu are used. Main aspect is given to the different Mg/Si ratios of the investigated alloys. Observed exothermic and endothermic peaks, accompanying the formation or dissolution of precipitates,...

article

Modelling the dynamic recrystallization in C–Mn micro-alloyed steel during thermo-mechanical treatment using cellular automata

Alexander Timoshenkov, Piotr Warczok, Mihaela Albu, Juergen Klarner, more

Computational Materials Science > 2014 > 94 > Complete > 85-94

This work presents approaches for the description of the microstructure evolution in a C–Mn micro-alloyed steel using cellular automata (CA) during thermo-mechanical treatment. The developed probabilistic-based model integrates the effects of the individual metallurgical phenomena related to the hot rolling process, such as hot deformation, dynamic recrystallization (DRX) and precipitation state,...

article

Thermo-kinetic prediction of metastable and stable phase precipitation in Al–Zn–Mg series aluminium alloys during non-isothermal DSC analysis

Peter Lang, Tomasz Wojcik, Erwin Povoden-Karadeniz, Ahmad Falahati, more

Journal of Alloys and Compounds > 2014 > 609 > Complete > 129-136

The technological properties of heat treatable Al–Zn–Mg alloys originate in the morphology and distribution of metastable particles. Starting from the solution-annealed condition, this paper describes the precipitate evolution during non-isothermal temperature changes, namely continuous heating differential scanning calorimetry (DSC) analysis. The distribution and the morphology of the metastable...

article

The microstructure of heat-treated nickel-based superalloy 718Plus

Lawrence Whitmore, Mohammad Reza Ahmadi, Laure Guetaz, Harald Leitner, more

Materials Science & Engineering A > 2014 > 610 > Complete > 39-45

The microstructure of thermally aged nickel-based 718Plus superalloy is investigated using transmission electron microscopy (TEM). Solution annealing at 980°C for 30min is followed by either the standard quenching to room temperature or quenching directly to 788°C, before isothermal aging at 788°C for four hours. Micro-hardness and yield strength are measured to compare the effects of the two variations...

article

Assessment of parameters for precipitation simulation of heat treatable aluminum alloys using differential scanning calorimetry

Ahmad FALAHATI, Jun WU, Peter LANG, Mohammad Reza AHMADI, more

Transactions of Nonferrous Metals Society of China > 2014 > 24 > 7 > 2157-2167

Differential scanning calorimetry (DSC) has been used extensively to study different solid state reactions. The signals measured in DSC are associated with the growth and dissolution of different precipitates during a specific heat cycle. The time-temperature dependence of heat cycles and the corresponding heat flow evolution measured in the sample by DSC provide valuable experimental information...

article

Microstructural investigation of thermally aged nickel-based superalloy 718Plus

Lawrence Whitmore, Mohammad Reza Ahmadi, Martin Stockinger, Erwin Povoden-Karadeniz, more

Materials Science & Engineering A > 2014 > 594 > Complete > 253-259

The effects of thermal aging upon the nickel-based 718Plus superalloy are investigated and modelled. Yield strength and micro-hardness measurements are made after solution annealing and after aging at 788°C for 4h. In order to explain the differences in strength and hardness, a detailed investigation of the microstructure is performed using transmission electron microscopy. The size and phase fraction...

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INFONA - science communication portal

Search results for: Ernst Kozeschnik

Advanced Thermo-mechanical Process for Homogenous Hierarchical Microstructures in HSLA Steels

Temperature-dependent strain hardening, precipitation and deformation-induced microstructure evolution in AA 6061

Phase evolution and carbon redistribution during continuous tempering of martensite studied with high resolution techniques

Analysis of the Temperature and Strain-Rate Dependences of Strain Hardening

Carbide Precipitation in 2.25 Cr-1 Mo Bainitic Steel: Effect of Heating and Isothermal Tempering Conditions

The Cr-Nb-Si system: Improved thermodynamic modelling and its use in simulation of Laves phase in steel

Dissolution of hardening phases during deformation in an A6061 Aluminium alloy

Modelling hydrogen migration and trapping in steels

CALPHAD-based alloy design for advanced automotive steels – Part II: Compositional and microstructural modification for advanced carburizing steels

A Model for Static Recrystallization with Simultaneous Precipitation and Solute Drag

[O16] Thermodynamics of the Pd-Mn system and phase stability of L10-based Pd1-xMn1-yFex+y

[P90] Thermodynamics of carbon trapping at dislocations in martensite

Modeling precipitation thermodynamics and kinetics in type 316 austenitic stainless steels with varying composition as an initial step toward predicting phase stability during irradiation

Modelling the influence of austenitisation temperature on hydrogen trapping in Nb containing martensitic steels

Simulation of the effect of composition on the precipitation in 6xxx Al alloys during continuous-heating DSC

Modelling the dynamic recrystallization in C–Mn micro-alloyed steel during thermo-mechanical treatment using cellular automata

Thermo-kinetic prediction of metastable and stable phase precipitation in Al–Zn–Mg series aluminium alloys during non-isothermal DSC analysis

The microstructure of heat-treated nickel-based superalloy 718Plus

Assessment of parameters for precipitation simulation of heat treatable aluminum alloys using differential scanning calorimetry

Microstructural investigation of thermally aged nickel-based superalloy 718Plus

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