Foundry Al-Mg alloys play an important role in overall foundry industry of light metals due to their outstanding properties, although their solidification mechanism has not been clearly determined. Solidification overview of multicomponent technical AlMg9 alloy was obtained in this work. One of significant achievement was application of "disturbed" solidification method by quenching at exactly determined temperature to obtain frozen microstructure. This method enables correlation between characteristic temperatures of phase transformations and corresponding characteristics of microstructure constituent. Mathematical expression related to the quenching temperature and time enable prediction of microstructure development during solidification of AlMg9 alloy. Chemical composition determination of particular phases, carried out by energy dispersive spectroscopy (EDS), resulted in identification of Alx(MnFe)ySiz, Mg2Si and Al8Mg5 phases. Temperature and time solidification sequence were determined and compared to the predicted ones, by phase diagram modeling. The change of particular phase ratio during solidification process was established also by mathematical modeling. These models offer an oversight of the required solidification microstructure development.K e y w o r d s : Al-Mg alloy, solidification, quenching, simultaneous thermal analysis, microstructure development

Commercial AlSi7Mg alloy represents the usual choice for complex geometry casting production. The market imperative to improve mechanical properties imposed the design of new chemical composition of AlSi7MgCu alloy with high content of Cu (up to 1.435 wt.%). This represents a challenge in order to achieve advanced properties. The interaction of a number of alloying (Si, Mg, Cu) and trace elements (Fe, Mn) influenced a wide range of complex reactions occurring and therefore leading to intermetallic phase precipitation. The characterization of novel chemical composition interaction and its solidification sequence was achieved by modelling an equilibrium phase diagram, simultaneously performing both thermal analysis and metallographic investigations. Copper influence was indicated in the whole solidification process starting with infiltration in modified Chinese script phase Al15(Fe,Mn,Cu)3Si2, beside common intermetallic Al5FeSi. Copper addition encourages formation of compact complex intermetallic phases Al5Cu2Mg8Si6 and Al8(Fe,Mn,Cu)Mg3Si6. Solidification ended with secondary eutectic αAl + Al2Cu + βSi. Microstructure investigation allows volume reconstruction of the microstructure and distribution of particular phases. Chemical compositions enriched in copper content and developed microstructural constituent through solidification sequence of AlSi7MgCu alloy contribute to a significant increase in mechanical properties already in an as-cast state.

Microstructure development and possible interaction o f present elements have been determined in charge material o f EN AB AlSi9Cu3 quality. Literature review enables prediction o f solidification sequence. Modelling o f equilibrium phase diagram fo r examined chemical composition has been performed, which enables determination o f equilibrium solidification sequence. Microstructural investigation indicated distribution and morphology o f particular phase. Metallographic analysis tools enable exact determination o f microstructural constituents: matrix aAr eutectic a u+ fsr iron base intermetallic phase -AfFeSi, A l/F e ,M n )C u S iw and/or Al/Fe,M n) M g,CuSin, and copper base phases in ternary eutectic morphology AI-AfCu-Si and in complex intermetallic ramified morphology Al/F e,M n)vMg,SiuCuw. Microstructure development examination reveals potential differences due to copper content which is prerequisite fo r high values o f final mechanical, physical and technological properties o f cast products.

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The subject of the paper is heat exchange in the system casting -riser -ambient. The examinations were focused on evaluating temperature dependence of the coefficient of heat exchange from mould external surface (or from riser thermally insulated surface) to ambient. The examinations were carried out for the surface temperatures of 200-800• C. On the basis of the performed examinations it was stated that the relationship α ext.e f f vs. surface temperature can be described by a polynomial of 3 rd degree with accuracy of 90-95% and that the α ext.e f f coefficient significantly depends on the examined material mass density.Keywords: casting, casting mould, solidification modelling, heat exchange coefficient Praca dotyczy określenia temperaturowej zależności współczynników, opisujących intensywność wymiany ciepła w ukła-dzie odlew -nadlew -forma odlewnicza -otoczenie. Na podstawie pomiarów temperatury i bilansów cieplnych określono wartości sumarycznego współczynnika wymiany ciepła do otoczenia z powierzchni nagrzanej warstwy ochronnej (izolacyjnej) górnej powierzchni nadlewu, w zakresie temperatury 200-800• C. Uzyskano zależności o stosunkowo dobrym dopasowaniu, na poziomie R 2 (0.9-0.95). Porównawcza analiza wyników dla dwóch zbadanych materiałów, różniących się gęstością masy i pojemnością cieplną, wykazała, iż nie ma prostej zależności pomiędzy nimi, to jest wartość sumarycznego współczynnika wymiany ciepła nie zmienia się wprost proporcjonalnie do iloczynu gęstości masy i pojemności cieplnej. Uzyskane wyniki mogą być wykorzystane do określenia warunków początkowo-brzegowych w konstruowanych modelach numerycznych wymiany ciepła w układach odlew -nadlew -forma odlewnicza -otoczenie.