The purpose of master’s thesis is characterization of mechanical properties of high pressure die cast parts from alloy AlSi9Cu3 with dependence on chemical composition, nucleation potential and local cooling rate. For that purpose, the castings from industrial technological praxis were systematically picked and from that castings probes were extracted for characterization of mechanical properties. For characterization of mechanical properties, we have planned special non-standard cylinders on which compressive tests were carried out. The uniqueness of this research is that the diameters of designed cylinders was adjusted to the actual wall thickness of the casting. This is important because the solidification of metal in die cavity is complex, on the surface cooling rates are the highest and, in the centre, the lowest. During the process in the experimentational phase chemical composition was systematically monitored. Parallel to sequence of casting on high pressure casting machine gravitational casting of the same alloy was carried out in special measuring cells with instrumented thermocouple (Simple thermal analysis was conducted). Samples for metallographic analysis from the casting for different wall thicknesses as well as from STA samples and samples for chemical composition were extracted. We have discovered that with increasing cooling rates mechanical properties of alloy AlSi9Cu3 are increasing in the area of cooling rates from 4 K/s to 125 K/s. Further it was found that nucleation potential has no clear effect on crystallization at very high cooling rates which are typical for HPDC. The key influence on size of microstructural components and on mechanical properties has cooling rate as well as micro and macro defects which originate from HPDC process itself. Those are gas and shrinkage porosities and non-metallic inclusions.
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