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Evaluation of eutectic growth in grey cast iron by means of inverse modelling
Department of Mechanical Engineering, Jönköping University, Jönköping.
2003 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 16, no 1-3, 301-306 p.Article in journal (Refereed) Published
Abstract [en]

Computer simulation of casting becomes a valuable tool for developing advanced materials and casting components. Recent investigations and validation work on simulated cast components reveal the necessity of reliable analyses methods to determine solidification behaviour and to extract parameters for kinetic models to use at simulation of complex cast iron materials. The paper will present an inverse modelling method for determination of eutectic growth. The method include an experimental part proper to investigate simultaneously the solidification at three different cooling rates while the cast material has the same metallurgical origin, and a computational part for calculation of grow kinetics. Validation of the inverse method is made together with simulation. The inverse modelling of eutectic growth in grey iron indicates that chemical composition, type and amount of inoculants and cooling condition are strongly influencing the eutectic growth condition and gives different eutectic growth coefficients. By invoking a generalized KJMA* equation, the shape of the growing eutectic interface can be predicted. Deviation from perfectly spherical growth in real solidification cases is the source of variation of eutectic growth coefficients. The results of the inverse model are valuable to simulate differences in solidification behaviour in differently treated grey iron melts. * KJMA is the abbreviation of the name of the famous scientists Kolmogorow, Johnson, Mehl and Avrami who developed and applied the equation.

Place, publisher, year, edition, pages
2003. Vol. 16, no 1-3, 301-306 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-87059OAI: oai:DiVA.org:liu-87059DiVA: diva2:584579
Available from: 2013-01-09 Created: 2013-01-09 Last updated: 2017-12-06
In thesis
1. On microstructure formation and mechanical properties in grey cast iron
Open this publication in new window or tab >>On microstructure formation and mechanical properties in grey cast iron
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A major user of cast components is the automotive industry, where the functionality of the components is related to environmental demands. Internal combustion engines are constantly being improved to emit less pollution. A vital part in this development is to increase the material properties of engine components during their life cycle. In particular, cylinder heads, cylinder blocks and piston rings for diesel engine are produced in grey cast iron. Cast iron is expected to be in use far into the foreseeable future, due to favourable properties and low production costs. This work has been devoted to study microstructure formation, the tensile properties of cast iron and to some extent defect formation.

The microstructure develops during solidification and solid state transformations. An inverse thermal analysis method was developed to study the kinetics of the microstructure formation. The inverse thermal analysis used, the Fourier method, analyses the cooling curves of two thermocouples to study the solidification or transformation. To decrease experimental errors, simulations have been done and the cooling curves were analysed. The best results were obtained when the thermocouples were placed close to each other.

With the help of the thermal analysis a time dependent and fading nucleation law of the eutectic cells was found to fit the experimental results best. The experiments were made by multiple thermal analyses, and six different types of inoculants were investigated. The eutectic growth behaviour during solidification was evaluated with inverse thermal analysis, and it was found that commercial inoculants not only affect the eutectic nucleation but they also control the eutectic growth rate.

Models of densities and volume changes are an integral part of a microstructure simulation of cast irons. These models are important for the inverse thermal analysis and an understanding of the porosity and expansion penetration in cast iron.

The tensile strength of grey cast iron has been discussed by examining the fracture mechanism of the material at failure. The ultimate tensile strength is a result of the intimate collaboration between the graphite flake and the primary phases. Several parameters, including the graphite morphology, carbon content, inoculation and cooling conditions influence the ultimate tensile strength by offseting the equilibrium between the major constituents, the graphite flakes embedded in the primary metallic matrix. A model to predict the ultimate tensile strength is developed based on the interpretation of the stress intensity behaviour in a eutectic cell.

The models developed for nucleation, eutectic growth and prediction of tensile strength were introduced into a casting simulation program. Mould filling, solidificauon, microstructure development and tensile strength of a complex. shaped cylinder head were simulated.

Place, publisher, year, edition, pages
Jönköping: Jönköping, 2004. 25 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 871
Keyword
grey iron, nucleation, primary austenite, eutectic cell, growth rate, inoculation, thermal analysis
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-23153 (URN)2557 (Local ID)91-7373-939-1 (ISBN)2557 (Archive number)2557 (OAI)
Public defence
2004-05-14, Föreläsningssal E 101, Ingenjörshögskolan, Jönköping, 10:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-09

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