ABSTRACT. In this study we used the cast TATUR samples that promotes the formation of an AlSi alloy porosity through a variable temperature gradient from top to bottom of the specimen. The die (permanent mold) was instrumented by thermocouples in order to follow the cooling of the specimen in several emplacements. Thermal analyses via cooling curves have been correlated to the microstructural data (SDAS measurement). Samples were cut from all castings and analyzed by optical microscopy in order to get the Secondary Dendrite Arm Spacing (SDAS) variation in function of cooling rates in the casting. The present work shows the effect of various pre-heating mould temperature and melt treatment on secondary dendrite arm spacing.

Abstract. Porosity is one of the major defects in aluminum castings, which is induced by several mechanisms (solidification shrinkage and gas segregation). One of the methods for complex evaluation of macro and micro porosity in Al-Si alloys is Tatur test technique. This article deals with evaluation of porosity with help of Tatur test for an Al-Si alloy. The simulation tests were conducted using commercial FEM based software. The simulation results obtained using ProCAST software will be compared with experimental measurement of porosity. Comparison has shown good agreement of simulation and experiment in predicting and localizing the major defects of shrinkage except for slump defect in top part of the casting which would mean, that the solidification modeling included in the tested software does not reflect phenomena responsible for the solidification processes in real castings properly. Further tests, with different types of software and more fundamental studies on the solidification process modeling would be desirable.

In this study we used the cast TATUR samples that promotes the formation of an AlSi alloy porosity through a variable temperature gradient from top to bottom of the specimen. The die (permanent mold) was instrumented by thermocouples in order to follow the cooling of the specimen in several emplacements. Thermal analyses via cooling curves have been correlated to the microstructural data (SDAS measurement). Samples were cut from all castings and analyzed by optical microscopy in order to get the Secondary Dendrite Arm Spacing (SDAS) variation in function of cooling rates in the casting. The present work shows the effect of various pre-heating mould temperature and melt treatment on secondary dendrite arm spacing.

In the present research, effects of titanium addition as grain refiner combined with casting parameters on the porosity in the AlSi9 alloy was studied. Porosity was investigated via TATUR test. The casting parameters studied are: pouring temperature and initial mold temperature. The total porosity was experimentally quantified by densimetry method. A small decrease in porosity value was observed with increasing the pouring temperature from 700 to 800 °C. It has been found that the effect of grain refinement by titanium addition on the porosity is more important, when the liquid metal was poured at 700 °C. Specimen poured in preheated mold at 300 °C present small values of porosity.