Master‘s thesis deals with the forming of hypereutectic aluminium alloys using sacrificial coatings. Literature research is focused on analysing the characteristics of aluminium and its alloys. Attention is also focused to the heat treatment of aluminium alloys and the influence of alloying elements on these alloys. Analysis of characteristics and increase the useful properties of Al - Ni alloys is another object of literary research. Attention is also focused to the analysis of thermal spraying methods by focusing on the principle of individual methods and the characteristics of the coatings made by these methods. The object of experimental part is to prepare the hypereutectic aluminium alloys using sacrificial nickel based coatings. This is an unconventional manufacturing process comprising coating the surface of the aluminium substrate with using HVOF technology and subsequent thermal exposure. Furthermore, the work deals with the metallographic evaluation of prepared samples with a particular focus on the influence of temperature and time of heat treatment on the final structure of the experimental samples.

Techn. Universiẗat, Diss., 2001--Darmstadt.

Hypoeutectic Fe-C and Fe-C-Si model alloys were produced at different solidification conditions. Copper mold casting yields low cooling rates promoting the formation of a eutectic microstructure characterized by two morphologies: elongated cementite plates and a rod structure growing perpendicular to the plates, i.e. austenite rods in a cementite matrix. Electron beam surface remelting generates a mainly plate-like eutectic due to rapid solidification. The microstructures were characterized by light-optical microscopy and electron backscatter diffraction (EBSD). The latter allows for a spatially resolved investigation of the growth crystallography of the eutectic phases. Thereby, a possible existence of crystallographic orientations relationships between cementite and austenite within the plate-like eutectic was assessed experimentally. The eutectic phases were found to grow largely crystallographically independently. Moreover, ferrite and eutectic cementite within the decomposed eutectic microstructure comply frequently with the Bagaryatsky or the Pitsch-Petch orientation relationship. Complementary X-ray diffraction (XRD) analysis reveals a pronounced cementite {002} texture in the microstructure produced by mold casting. Characteristic changes in the lattice parameters indicate that as-cast cementite is non-stoichiometric.