Development of an Experimental Setup to Investigate Influences on Component Distortion in Gravity Die Casting and a First Variation of Temperature Control Strategy

Distortion (1), residual stresses and hot cracks can facilitate significant decreases in quality characteristics of casting products. Their reduction by a suitable component design (2) and process control is therefore desirable. In the casting process, these characteristics are assumed as a result of the combination of solidification shrinkage paired with the local self-feeding and the geometric constraints imposed on the component by the mold. In gravity die casting (3) of aluminum (4) with thermally well conducting and rigid metal molds, the control of solidification through a localized adjustment of the heat balance (5) appears to be a suitable approach to minimize these effects. The development of an experimental setup for the assessment of the interdependencies of the alloy, casting geometry and cooling are described in this work. A first series of experiments with A356 aluminum alloy and the introduction to the different methods of evaluation are presented. Furthermore, an approach to improve the understanding of the underlying mechanisms is outlined.

REFLECTIVITY OF ANODISED AL-SI ALLOY SURFACE OF BELT PULLEYS USED IN COMBUSTION ENGINES

The recent trend of using aluminium alloys instead of steel has reached the transportation industry, where increasingly, more parts are made of aluminium. An example is the belt pulley, applied for combustion engines for energy transmission. This part should be strong, durable, and lightweight. Aluminium-silicon alloys are a good choice, moreover, even when the surface is anodised, also because of their moderate inertia control and excellent wear characteristic during mechanical operations. Since aluminium is lightweight yet mechanically durable and anodised, it is an ideal belt pulley to use, especially in high-temperature operations. However, the main question is what type of Al-Si alloy, casting method and anodisation method should be used in terms of energy adsorption, having long-term properties for a lifetime, has to be applied. For this reason, this paper presents the influence of the chemical composition, casting method and anodising parameters on the structure and thickness of the anodic layer produced on aluminium alloys, as well as on the albedo value as an ability to reflect or absorb light. The aluminium alloys, AlSi12Cu1 and AlSi9Cu3, were used as research materials, obtained using different casting methods. The goal of this work was to determine the optimal combination of the anodisation conditions and materials for maximising the reflectivity factor of the surface, as a very important factor, determining the energy amount absorbed by an anodised surface. For further improvement of these surface properties as well as for enhancement of the properties and strengthen the material produced with different aluminium alloys production methods, different alloying additives were added. In addition, the mechanical properties of the surface layer were measured, where a remarkable hardness increase was obtained, and the best combination in form of AlSi12Cu1 high pressure cast was found with the highest albedo factor among all tested surface variants.

Consumption of Entrained Gases Within Bifilms During a Mg-Alloy Casting Process

The formation of entrainment defects, (also known as double oxide film defects or bifilms), caused by the entrapment of a doubled-over surface oxide film containing a small amount of local atmosphere, has been investigated by combining practical experiments using a commercial-purity Mg-alloy under protective gases, with theoretical thermodynamic calculations. Evolution of the entrainment defects was studied, and a double-layered structure of their oxide films was found, which was different from the single-layered structure of the Mg-alloy melt surface films that have been previously reported. A pore gas analyzer was used to analyze the gas trapped within the defects from which H2 and N2 (from the air) were detected. It was found that entrapped gases can be depleted through reactions with the surrounding liquid Mg-alloy, resulting in the oxide films growing together in the melt. Transformation of the entrained gas to solid-phase compounds could reduce the void volume of the defects, thus probably diminishing the negative effect of the entrainment defects on the quality of castings.

Optimization of Magnesium Alloy Casting Process: An Integrated Computational Materials Engineering (ICME) Approach

Traditional casting process optimization usually adopts empirical trial and error method. Process parameters were modified repeatedly within a certain range until a satisfactory solution is obtained, which is costly and inefficient. Therefore, based on integrated computational materials engineering, Magnesium Alloy Simulation Integrated Platform (MASIP) was constructed. MASIP completed the automatic operation of the entire simulation process from the CAD model data input to the process-microstructure-performance. It realized the rapid optimization simulation prediction of process-microstructure-performance, and solved the problems of long cycle and low efficiency of traditional process optimization. This paper studied the low-pressure casting optimization process of magnesium alloy thin-walled cylindrical parts based on MASIP. The calculation took casting temperature, mold temperature and holding pressure as the optimized variables, and the yield strength of the casting as the target variable. The experimental results showed that MASIP can fairly complete the structure simulation and performance prediction of castings, greatly reduce the time cost of the calculation process, and improve the efficiency of process optimization.

Solidification and Microstructure Simulation of A356 Aluminum Alloy Casting

To obtain an A356 aluminum alloy casting with a uniform structure and no internal shrinkage defects, ProCAST software is used to set different filling and solidification process parameters for an A356 aluminum alloy casting with large wall thickness differences, And multiple simulations are conducted to obtain optimized casting process; then, based on the process, the microstructure of the thickest and thinnest part of the casting are simulated. The size, morphology, and distribution of the simulated microstructure of the thinnest part and the thickest part of the casting are very similar. The simulated microstructure is similar to that of the actual casting. This shows that castings with uniform structure and no internal shrinkage defects can be obtained through the optimized casting process .