Papers by Author: Horst Cerjak

Paper TitlePage

Authors: Ernst Kozeschnik, Bernhard Sonderegger, Ivan Holzer, Joachim Rajek, Horst Cerjak
Abstract: Precipitates are the key ingredient for the strength of heat treatable alloys. To optimize the mechanical properties of alloys it is important to know the response of precipitates to thermomechanical treatments. In the past, application of computer models to describe the evolution of precipitates in the course of these processes has proven difficult due to the complexity of the problem. In this work, a new model based on a mean-field representation of precipitates in a multicomponent matrix is applied to heat treatments of steels. Example simulations are presented for a 9- 12% Cr ferritic/martensitic heat resistant steel for power plant application and a complex tool steel with both carbides and intermetallic phases using the software MatCalc. The predictions of the model are verified on experimental results and the potential application to industrial heat treatment simulation is discussed.
Authors: Horst Cerjak, Gerhard Dimmler, Ivan Holzer, Ernst Kozeschnik, Peter Mayr, Cornelia Pein, Bernhard Sonderegger
Abstract: The research activities on ferritic / martensitic 9-12% Cr steels at the Institute of Materials Science, Welding and Forming (IWS) are represented by a network of interacting projects focusing on mechanical properties of base and weld metal, microstructural characterisation of creep and damage kinetics, weldability, microstructure analysis in the course of creep, modelling of precipitation and coarsening kinetics, simulation of complex heat treatments and the deformation behaviour under creep loading. The individual projects are briefly described and the conceptual approach towards a quantitative description of the creep behaviour of 9-12% Cr steels is outlined.
Authors: Peter Mayr, T.A. Palmer, J.W. Elmer, Horst Cerjak
Abstract: A basic requirement for the production of large power plant components from ferritic/martensitic 9-12% Cr steels is good weldability. Weldments in these steels are often reported as the weak spots. In this work the weldability of a creep resistant 9% Cr steel is discussed. Different methods are utilized to characterize the microstructural evolution during different welding cycles and the following post weld heat treatment, as well as the resulting mechanical properties. Heat affected zone (HAZ) simulation using a thermo-mechanical testing device GLEEBLE 1500 is performed to study the microstructural evolution and changes in the mechanical properties in the different parts of the HAZ. Specimens exposed to peak temperatures higher than 1150°C showed a minimum of impact toughness after post weld heat treatment (PWHT). In situ X-ray diffraction experiments with synchrotron radiation are used to observe phase transformations during heating to elevated temperatures, where delta ferrite formation was observed at temperatures higher than 1250°C.
Authors: Horst Cerjak, P. Hofer, B. Schaffernak
Authors: Mehran Maalekian, M.L. Lendinez, Ernst Kozeschnik, Hans P. Brantner, Horst Cerjak
Abstract: The welding continuous cooling transformation (WCCT) behavior of eutectoid carbon steel was investigated in different peak temperatures and in the undeformed and deformed conditions. The corresponding WCCT and welding continuous cooling compression transformation (WCCCT) diagrams were constructed by means of dilatometric and metallographic analyses in addition to hardness measurements. It was found that the higher austenitizing temperature slightly accelerates pearlitic transformation, i.e., it shifts the WCCT diagram to shorter times. Furthermore, heavy hot deformation of austenite could strongly promote the formation of pearlite, that is, the WCCCT diagram moved toward the top left corner compared to the WCCT diagram, while martensite start temperature was lowered slightly, which is a characteristic of a displacive transformation mechanism.
Showing 1 to 6 of 6 Paper Titles