Papers by Keyword: Aluminium Casting Alloy

Abstract: The contribution describes changes in morphology of structural parameters in recycled (secondary) AlSi9Cu3 cast alloy microstructure. These changes depended on different temperatures of artificial aging. The T6 heat treatment, which was used for affecting the structural parameters morphology, consisted of solution treatment at temperature 515 °C with holding time 4 hours, water quenching at 40°C and artificial aging at different temperatures 130 °C, 150 °C, 170 °C, 190 °C and 210 °C with different holding time 2, 4, 8, 16 and 32 hours. The morphology of structural parameters was observed using combination of different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy - SEM upon deep etching). The different temperatures of artificial aging led to changes in microstructure include the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al₂Cu).

Abstract: Aluminum die casting components are widely used in vehicle constructions because they satisfy the conflicting requirements between weight reduction and mechanical property improvement. However, the analysis of deformation and damage behavior of aluminum cast components is very complex, since local mechanical properties in the components are inhomogeneous as a consequence of spatial distribution of microstructure. For crash simulation it is necessary to well predict the damage behavior which is strongly influenced by micro-defects especially by cast pores. The conventional continuum mechanics approaches often fail due to the statistical character of cast pores. In this work the Markov random field model (Ising) is used to describe the pore morphology. Markov random field classes are defined by porosity (macroscopic property) and equivalent pore size (microscopic property) and determined by micro computer tomography (CT) analysis.A multi scale approach was applied to map the results of the stochastic model to the FE models, which results in a distribution of porosity. A porosity dependent continuum model was developed based on results of representative volume elements with variation of porosity. It was shown that the continuum model with porosity distributions from the Ising model as initial conditions captures well the spatial material properties (i.e. fracture strain) and their variations in the bridging scale.

Abstract: The Quality Index is a useful tool allowing to assess the metallurgical quality of aluminium AlSiMg foundry alloys (AlSi7Mg03/AlSi7Mg06, or A356/357 in North America). Its value, calculated from the ultimate tensile strength and elongation, increases with the metallurgical quality of the casting, i.e. with finer dendrites, lower microporosity, lower iron content and cleaner metal. This Quality Index does not depend on the degree of temper applied during the heat treatment (aging time and temperature). This paper will briefly explain how solidification modeling can provide the local value of the Quality Index, via the secondary dendrite arm spacing and level of microporisity calculated from the predicted values of the local solidification time and solidus velocity. The validity of the predictions has been assessed against the properties of tensile specimens excised from parts of different geometries produced by a variety of casting processes, as reported in the literature. The case study of a race car bell housing poured by two processes, namely gravity sand casting (GSC) and low pressure die casting (LPDC, or LPPM for Low Pressure Permanent Mold in North America), will be the focus of the present paper. The Quality Index has been measured and predicted at 3 locations in the castings after a T6 temper was applied which resulted in a minimum elongation of 5% for both the GDC and LPDC bell housings. Metallographic examination and image analysis allowed to quantify the superior metallurgical quality of the LPDC housings when compared to their GDC competitors.

Abstract: Internal stresses in aluminum casting alloy were measured by the neutron stress measurement method with the apparatus RESA in Japan Atomic Energy Agency (JAEA). In usual cases, coarse crystal grains are included in aluminum casting alloy. These coarse crystal grains make it extremely difficult to estimate the internal stresses by the neutron diffraction [1]. The two problems arise because of the existence of the coarse crystal grains. The first problem is the production of an unstable diffraction profile in the necessary direction. The second is the edge effect which is generated by the overhang of the coarse crystal grains from the neutron irradiation area (gage volume). In this study, two kinds of new techniques used were proposed to resolve these problems. Firstly, the elastic theory based on the sin2ψ method is shown. Diffraction peaks in several directions were found by use of the rocking curve method. Following that, the lattice spaces in each principal direction were calculated from these diffraction peaks using the elastic theory. Secondly, the distribution of edge effect around the gage volume was measured using a small bit of copper single crystal. From this result, the edge effect was canceled out by the modified measurement method which was done symmetrically. Finally, the aluminum casting sample which included coarse crystal grains was set to the tensile testing machine on RESA’s measurement table and the applicability of these new techniques were confirmed experimentally.

Abstract: The economical and environmental effects of mass reduction through Al and Mg primary alloys substitutions for cast iron and steel in automotive components are discussed using M.F. Ashby’s penalty functions method. The viability of Mg alloy substitutions for existing Al alloy cast components is also considered. The cost analysis shows that direct, equal-volume, Al alloy substitutions for cast iron and steel are the most feasible in terms of the CAFE liability, followed by substitutions involving flat panels of prescribed stiffness. When the creation of CO2 associated to the production of Al and Mg is considered, the potential gasoline savings over the lifespan of the car compensate for the intrinsic environmental burden of Al in all applications, while electrolytic Mg substitutions for cast iron and steel are feasible for equal volume and panels only. Magnesium produced by the Pidgeon thermal process appears to be too primary energy intensive to be competitive in structural applications. Magnesium substitutions for existing Al alloy beams and panels are generally unviable. The current higher recycling efficiency of Al casting alloys confers Al a significant advantage over Mg alloys.

Abstract: Changes in tensile properties of A206 Al-Cu-Mg casting alloys containing trace amount of rare earth(RE) elements up to 0.2% were investigated and discussed in relation to the microstructural evolution. The A206 alloy with 0.1%RE shows higher values of ultimate tensile strength(UTS) and yield strength(YS) than A206 alloy at room and elevated temperatures up to 300oC, whereas no remarkable change is found in elongation with respect to RE addition. In view of X-ray diffractometry(XRD) and transmission electron microscopy(TEM), the improvement of tensile strength in the A206 alloy with 0.1%RE would be caused by higher number density of Al2Cu(q¢) strengthening precipitates.