Thixoforming is an emerging young technology to produce complex structural parts and near net shape components. Thixoforming stands for the forming of materials in the semi-solid state. One precondition for the thixoformability of materials is the minimum temperature range for the solidus-liquidus interval and the globulitic formation of the solid phase during the thixoforming process. Besides this other parameters like shape factor, contiguity, matrix character, melting interval, and phase distribution are important process parameters. Aluminium and magnesium alloys are the objectives of numerous investigations, but research activities concerning the thixoformability of steel alloys have been commenced recently. This article provides metallographic information on the relevant parameters of the steel X21OCrW12, taking into account the microstructural evolution and the establishment of a parameter field for forming this material in the semi-solid state. Untersuchungen zur Gefiigeentwicklung desStahles X210CrW12 im teilfliissigen Bereich. Ein Verfahren zur Herstellung komplexer, endabmessungsnaher Bauteile stellt das Thixoforming dar. Unter Thixoforming versteht man die Formgebung von Werkstoffen im teilflOssigen Bereich. Eine Voraussetzung fOr die Thixoformbarkeit von Werkstoffen ist die globulitische Einformung der noch festen Ge-fOgebestandteile im Temperaturbereich der Formgebung. Weiterhin sind auch Parameter wie Formfaktor, Kontlquitat, Matrixcharakter, Schmelzintervall und Phasenantellvertaute wichtige ProzeBkenngr6Ben. Seit Jahren findet Forschungsarbeit auf diesem Gebiet vornehmlich im Bereich der Aluminium-und Magnesiumlegierungen statt. Die Forschung auf dem Gebiet Thixoforming von Stahlwerkstoffen wurde in jOngerer Zeit begonnen. Dieser Artikel befaBt sich mit der Beschreibung der GefOgeentwicklung des Stahls X210CrW12 sowie der Aufstellung eines Parameterfeldes fOr das Thixoforming fOr diesen Werkstoff.
The austenite grain growth of a microalloyed steel was investigated via annealing experiments and phase-field simulations using the phase-field code Micress. The technique described in a previous work was enhanced and applied to an Nb, Ti microalloyed linepipe steel for the case of isothermal heat treatment between 1 050 and 1 200 8C. The input parameters for the phase-field simulations were deduced from physical models based on the results of isothermal holding experiments. A further improvement was the use of the software package MatCalc to simulate at a lower scale the coarsening of the pinning particles. The results of these simulations showed good agreement with the experimental results.
One important parameter for the processing of materials by semi-solid forming is the actual distribution of the solid and liquid phases in the semi-solid range. This parameter defines the process stability for the forming step. Therefore it is necessary to obtain information about the materials behaviour in the semi-solid state for different materials grades. This kind of information can be obtained by experimental studies in the interesting temperature range or by calculations with simulation programs using thermodynamic data validated by experiments. This work shows the results of experimental studies and thermodynamic calculations of the solidification and heat treatment behaviour of the aluminium alloy A319 and the steel X210CrW12. The experimental studies of solidification and heat treatment of these alloys were carried out using a differential thermal analysis system (DTA). The theoretical fraction of liquid content was calculated from the DTA signal by using a software module called Corrdsc. The experimental data obtained were used to validate the thermodynamic simulations of the solidification of semi-solid alloys. The simulations of the solidification process were carried out for equilibrium conditions, with the Scheil-Gulliver model as well as with diffusion calculations. The equilibrium and Scheil-Gulliver calculations were performed by the program Thermo-Calc, and the diffusion by the program DICTRA. The required thermodynamic and mobility data for multicomponent systems were taken from the data bases COST 507 light alloys, TCFE2000 Steel/Alloys and MOB2 mobility and from newly added data. The comparison of calculated phase transformations and fractions of liquid content with experimental data revealed a good agreement.
Modern high-strength low-alloy steels commonly contain microalloying additions of titanium, niobium or vanadium in different combinations in order to obtain the desired microstructure and mechanical properties. Titanium has a strong tendency to form TiN in the range of the solidus temperature. This has been reported to have a negative effect on the impact toughness of the material. Thermodynamic calculations showed that the titanium and nitrogen content and the titanium to nitrogen ratio determine if the formation of TiN takes place during solidification or in the solid state. These calculations where complemented by simulations of solidification using the Scheil – Gulliver model and DICTRA. The results were compared with microstructure investigations of plate and slab material with titanium contents between 0.003 wt.% and 0.015 wt.% using light-optical microscopy and electron probe microanalysis. While the formation of TiN particles cannot be ruled out even at the lowest Ti levels, the temperature of formation and the volume fraction varied significantly depending on the Ti content. With respect to the first results of this preliminary study, i. e. the comparison of equilibrium, Scheil and DICTRA calculations, it can be assumed that the Scheil model is the most appropriate one at present.
No abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.