Search results for: Erwin Povoden-Karadeniz

Items from 1 to 17 out of 17 results

article

Microstructure Characterization of Nickel Matrix Composite Reinforced with Tungsten Carbide Particles and Produced by Laser Cladding

Josef Domitner, Zahra Silvayeh, Ricardo Henrique Buzolin, Sabine Krisam, more

Advanced Engineering Materials > 24 > 11 > n/a - n/a

Detailed experimental characterization of a laser‐clad metal matrix composite (MMC) consisting of hard tungsten carbide particles embedded in a comparatively soft nickel‐based matrix is provided. Special focus of the investigations is placed on the relationship between the microstructure of the as‐deposited reinforcing particles and their hardness. Therefore, thermally induced dissolution of carbides...

article

Thermodynamic Modeling of the La-Co-O System

Wei-Wei Zhang, Erwin Povoden-Karadeniz, Huixia Xu, Ming Chen

Journal of Phase Equilibria and Diffusion > 2019 > 40 > 2 > 219-234

A thermodynamic modeling of phase diagrams and thermodynamic properties of the La-Co-O system is presented. Special attention is given to the perovskite LaCoO_3−δ phase, due to its outstanding practical importance. In addition to phase equilibria, defect chemistry and charge disproportionation of lanthanum cobaltite were considered during the modeling and are discussed with respect to their thermo-chemical...

article

Effects of Solid Solution Strengthening Elements Mo, Re, Ru, and W on Transition Temperatures in Nickel-Based Superalloys with High γ′-Volume Fraction: Comparison of Experiment and CALPHAD Calculations

Nils C. Ritter, Roman Sowa, Jan C. Schauer, Daniel Gruber, more

Metallurgical and Materials Transactions A > 2018 > 49 > 8 > 3206-3216

We prepared 41 different superalloy compositions by an arc melting, casting, and heat treatment process. Alloy solid solution strengthening elements were added in graded amounts, and we measured the solidus, liquidus, and γ′-solvus temperatures of the samples by DSC. The γ′-phase fraction increased as the W, Mo, and Re contents were increased, and W showed the most pronounced effect. Ru decreased...

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

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

Thermodynamic modeling of the Sr–Co–Fe–O system

Wei-Wei Zhang, Ming Chen, Erwin Povoden-Karadeniz, Peter Vang Hendriksen

Solid State Ionics > 2016 > 292 > C > 88-97

This paper reviews and assesses phase equilibria and thermodynamic properties of phases in the Sr–Co–Fe–O system, with a focus on oxides, especially the SrCo₁₋_xFe_xO₃₋_δ perovskite. In our work, the SrCo₁₋_xFe_xO₃₋_δ perovskite was modeled with a three-sublattice model, where the three sublattices correspond to the A, B and oxygen sites in an ABO₃ perovskite, respectively. A number of other important ternary...

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

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

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

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...

article

CALPHAD modeling of metastable phases in the Al–Mg–Si system

Erwin Povoden-Karadeniz, Peter Lang, Piotr Warczok, Ahmad Falahati, more

Calphad > 2013 > 43 > C > 94-104

In the framework of the CALPHAD approach, a thermodynamic assessment of the metastable phases in Al–Mg–Si alloys is presented. The early Mg–Si co-clusters are described as a regular solid solution phase. A split model of fcc-based ordering is used for Guinier–Preston (GP)-zones as suggested by the assessment of microstructural data. The model parameters are optimized based on new thermodynamic first-principles...

article

Experimental Phase Diagram Determination and Thermodynamic Assessment of the CeO₂‐Gd₂O₃‐CoO System

Toni Ivas, Erwin Povoden‐Karadeniz, Nicholas Grundy, Eva Jud‐Sierra, more

Journal of the American Ceramic Society > 96 > 2 > 613 - 626

New phase diagram data and a thermodynamic assessment of the CeO‐Gd₂O₃‐CoO system using the CALPHAD approach are presented. This information is needed to understand the surprisingly low sintering temperature (950°C–1050°C) of CeO₂‐based materials doped with small amounts of transition metal oxide (e.g., CoO). Experimental phase equilibria between 1100°C and 1300°C are reported based on the analysis...

article

Transmission electron microscopy of single and double aged 718Plus superalloy

Lawrence Whitmore, Harald Leitner, Erwin Povoden-Karadeniz, Rene Radis, more

Materials Science & Engineering A > 2012 > 534 > Complete > 413-423

The effects of single and double aging upon the ATI 718Plus Nickel superalloy are investigated. Double aging is found to produce an increase in hardness as compared to single aging, thus an extensive micro-structural study is performed to identify and understand the physical reasons for this. Precipitation of the γ′ phase is of particular interest in this case. Using transmission electron microscopy...

article

Lower Triassic sulphur isotope curve of marine sulphates from the Dolomites, N-Italy

Micha Horacek, Rainer Brandner, Sylvain Richoz, Erwin Povoden-Karadeniz

Palaeogeography, Palaeoclimatology, Palaeoecology > 2010 > 290 > 1-4 > 65-70

6 evaporite samples from the latest Permian to the late Lower Triassic have been sampled at marine carbonate sections in the Southern Alps. The sulphur isotope ratio of the sulphate has been determined to learn about the changes of the marine δ ³⁴ S ratio during the investigated period, as it is known from the literature that a profound change from depleted to heavily enriched δ ³⁴ ...

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