Processing Aspects for Improving Mechanical Properties in Aluminium Castings

• The relation between the process and mechanical properties in aluminium alloys for castings has been examined. The relation was hard to define since the spread in data was severe due to defects created in the casting process. To avoid such defects a gradient solidification equipment was built. With this equipment it is possible to re-melt and solidify meta! with good feeding during the solidification over a !arge range of solidification rates. The results show very good mechanical properties for several cast aluminium alloys. From this it is concluded that the casting processes used today are not designed in a way that utilises the inherent potential in mechanical properties of the material.The ingate system design has been found to be one of the most important factors that influence the mechanical properties in castings. In this work many experiments have been made in order to study the mould filling behaviour. By the use of a glass wall and a video camera the mould filling of a vertically parted vacuum-sealed sand mould was studied. By changing the ingate system design and studying the filling sequences a thorough knowledge of the melt behaviour in the ingate system during the filling of the mould could be obtained. This knowledge could be used in many foundries to improve the ingate system design in order to increase the quality ofthe castings.A filter in the ingate system has been found to be one of the best ways to improve the mould filling. The filter will however reduce the flow, rate and it is therefore important to know the magnitude of the flow reduction. In this work a new technology is presented which can be used to obtain optimum proper filter parameters, which are important to get accurate results from simulations.

Nyckelord

Aluminium

microstructure

mechanical properties

gradient solidification

mould filling

filter

filter parameter

casting simulation

TECHNOLOGY

TEKNIKVETENSKAP

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