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The effects of casting parameters on residual stresses and microstructure variations of an Al-Si cast alloy
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
2009 (English)In: Advances in X-Ray Analysis (CD-ROM), ISSN 1097-0002, Vol. 52, 553-560 p.Article in journal (Refereed) Published
Abstract [en]

Different casting parameters can change the microstructure and residual stresses of castings. The microstructure of Al-Si cast alloys is influenced by the morphology of silicon particles (shape, size and distribution), aluminum grain size and dendrite parameters. Dimensional changes resulting from casting caused by residual stresses can particularly affect the quality of near net shape castings. In this research, the influence of casting process parameters such as modification, superheat temperature, mould hardness and mould design on residual stresses and microstructure of an Al-Si-Mn alloy have been investigated. Experiments were conducted with different superheat, mould hardness, modification with Al-10Sr and two different casting designs. The micro structural changes associated with these parameters have been studied by optical microscopy, scanning electron microscopy and image analysis. The type and extent of residual stresses of all samples were determined using the sectioning method. The results show that all of the mentioned casting parameters have clear effects on residual stresses. The residual stresses decrease with lowered superheat, temperature and mould hardness. It was found that the residual stress increases both with adding a eutectic modifier and with change of casting design. It wasalso found that microstructure and mechanical properties are  influenced significantly by the mentioned parameter.

Place, publisher, year, edition, pages
Newton Square, PA, United States: International Centre for Diffraction Data (ICCD) , 2009. Vol. 52, 553-560 p.
National Category
Other Materials Engineering
URN: urn:nbn:se:liu:diva-60908OAI: diva2:359717
57th Annual Conference on Applications of X-ray Analysis Denver X-ray Conference (DXC), Denver, Colorado, USA, 4–8 August 2008
Available from: 2010-10-29 Created: 2010-10-29 Last updated: 2016-02-17Bibliographically approved
In thesis
1. On the Residual Stresses and Microstructure Formation of Aluminum-Silicon Cast Alloys
Open this publication in new window or tab >>On the Residual Stresses and Microstructure Formation of Aluminum-Silicon Cast Alloys
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cast aluminum-silicon alloys are being increasingly used in automotive and aerospace industries for critical structure applications because of their excellent castability, low density, acceptable mechanical properties and low cost. Different casting and heat treatment parameters largely affect the microstructure and residual stress of the components, which in turn, has a great impact on their mechanical properties. In cast components, residual stresses are those stresses which may remain in the casting after it has been removed from the mould. The magnitude and distribution of the residual stresses can be critical to performance and should be considered in the design of a component. This work has been devoted to study the microstructure formation, residual stresses, and mechanical properties of aluminum-silicon castings.

The effects of casting parameters on the microstructure of the selected alloys were investigated by means of optical and scanning electron microscopes. With the help of EDS, WDS, EBSD, and quantitative analysis techniques, it was found that solidification rate, modification, superheat, casting temperature can significantly affect the nucleation and growth, morphology and chemical composition of different phases. Based on the performed microsegregation analysis, a clear correlation between the concentration of silicon in the primary phase and cooling rate was found.

Tensile tests at room and elevated temperatures in addition to microhardness experiments were performed to analyse the behaviour of the alloys under mechanical loads. The results showed that elongation to fracture, modulus of elasticity, and ultimate tensile strength of the tested alloys are temperature dependent. Moreover, the obtained information was used to establish a good model for simulating the behaviour of the cast alloys, as well as the mechanical properties and residual stresses.

The type and magnitude of residual stresses were mainly evaluated by strain gauge, sectioning, thermal analysis methods, and was also simulated by finite element analysis using Abaqus software. It was found that casting parameters such as superheat, mould hardness, casting temperature, modification, and the casting geometry, can influence the accumulated residual stress in the component. The thermal treatment experiments also indicated that the base temperature of the cast part before fast cooling, maximum temperature difference within the component, and cooling water flow can influence the residual stress. Extensive simulation work done by Abaqus showed that the results obtained by simulation are in a reasonable relationship with the experimental measurements, considering the linearly elastic/linearly isotropically hardening plastic model.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 48 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1369
Al-Si alloys, residual stresses, microstructure, microsegregation, nucleation behavior, modeling
National Category
Engineering and Technology
urn:nbn:se:liu:diva-70117 (URN)978-91-7393-176-2 (ISBN)
Public defence
2011-09-07, A35, A-huset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2011-08-19 Created: 2011-08-19 Last updated: 2012-01-19Bibliographically approved

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