ON MODELLING OF MICROSTRUCTURE FORMATION, LOCAL MECHANICAL PROPERTIES AND STRESS – STRAIN DEVELOPMENT IN ALUMINIUM CASTINGS

Today, the industrial demands are to reduce product development time as well as costs of producing prototypes. In this context, virtual prototyping by numerical simulation offers an efficient way of lowering costs and shorten lead time. Castings are produced by a manufacturing method which inherently affects the component’s properties depending on design, metallurgy and casting method. The wall thickness influences the coarseness of the microstructure and the material will have properties depending on the local metallurgical and thermal histories. This is independent on the material, i.e. whether the casting is based on cast iron- or aluminium-alloys. The distribution of local properties in a casting might vary substantially which makes it difficult to optimize the casting with good accuracy. Often, mechanical simulations of the load situation are based on the assumption that the cast product has constant material properties throughout the entire casting. Thus, if the microstructure is determined or predicted at a given point, it gives the possibility to calculate the local material behaviour more realistically. The paper shows modelling and simulation of microstructure formation, related to mechanical properties as elastic modulus, yield stress, ultimate strength and elongation. In the present work, a test case of a complex casting in an aluminium alloy is considered including simulation of the entire casting process with focus on of microstructure formation, related to mechanical properties as elastic modulus, yield stress, ultimate strength and elongation as well as residual stresses. Subsequently, the casting is subject to service loads and the results of this analysis are discussed in relation to the predicted local properties as well as the residual stresses originating from the casting simulation.