The paper presents the research data on structure, phase composition, defect substructure state, and microhardness of surface layers in the piston alloy Al-10wt%Si-2wt%Cu irradiated by an electron beam with various energy densities and pulse times. An important finding to emerge from the study is that the processing by an electron beam with an energy density of 10 J/cm2 brings about slight surface melting, whereas a weak thermal impact of an electron beam hardly changes the phase composition. Once an energy density of an electron beam is set 30 J/cm2, intermetallic compounds dissolve and numerous micropores arise. Irradiating by an electron beam with an energy density of 50 J/cm2, randomly located microcracks are detected on the treated surface with no regard to a pulse time. A structure of high-speed cellular crystallization with cells from 500 to 600 nm forms in the surface layer. A thickness of the modified layer is related to a beam energy density. As a beam energy density goes up, a thickness of a high-speed cellular crystallization layer increases. Atoms of Si, Cu, Ni, as well as a small quantity of Fe and Mg are detected in the surface, in thin layers surrounding crystallization cells. In a layer 60-80 μm below the irradiated surface, in material between high-speed crystallization cells, there are Si atoms and an insignificant number of Cu atoms. An analysis of a deeper material part has shown a structure similar to the as cast alloy. A drop of microhardness – if compared with the as cast material – is reported at an energy density of 10 J/cm2 because an energy amount supplied by an electron beam to the alloy surface is insufficient for melting of the material and dissolution of the intermetallic phase. A raise of a beam energy density up to 20-50 J/cm2 causes a max increase of microhardness up to 1.13 GPa for 40 J/cm2, 50 μs, and up to 1.16 GPa for 40 J/cm2, 200 μs.
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W publikacji zaprezentowane zostały wyniki przemysłowej (w Federal-Mogul Gorzyce S.A., dawnej WSK Gorzyce) optymalizacji procesu obróbki cieplnej (starzenia). Przedmiotem badań były tłoki silnika spalinowego, odlewane ze standardowego około eutektycznego siluminu stopowego typu AlSi12CuNiMg. Głównym celem badań był dobór optymalnych parametrów (temperatury i czasu) starzenia tak ze względu na twardość, jak też stabilność wymiarową tłoków. Dodatkowym celem niniejszej prezentacji jest pokazanie, iż niektóre procedury matematycznego-statystycznego modelowania i optymalizacji mogą być w sposób prosty i efektywny – szczególnie z zastosowaniem techniki komputerowej – wykorzystane przy sterowaniu odlewniczymi procesami produkcyjnymi. Artykuł został napisany na bazie rezultatów uzyskanych przy realizacji projektu badawczego Nr 9 9493 91 92 (nr umowy 370/S6/92/020) pt. „Stabilizacja materiałów i geometrii tłoków silników spalinowych” realizowanego na zlecenie KBN.
EN
The study gives the results of optimising the heat treatment process (ageing) carried out under industrial conditions at Federal-Mogul Gorzyce S.A. (former WSK Gorzyce). The subject of trials were pistons for POLONEZ car engine cast from standard around-eutectic alloyed silumin of the type AlSi12CuNiMg. The main object of the studies was the choice of optimum parameters (temperature and time) of the ageing heat treatment, taking into account the hardness and dimensional stability of pistons. An additional goal of this presentation was to prove that some procedures adopted in mathematical and statistic modelling and optimisation can be in a simple and effective way, specially when using computer technique, applied in control of foundry production processes. The study was made basing on the results obtained during execution of Research Project No. 9 9493 91 02 (contract no. 370/S6/92/020) entitled: „Stabilising materials and geometry of pistons for I.C. engines”, supervised by the State Committee of Scientific Research.
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