Papers by Author: Witold T. Kierkus

Abstract: The latent heat of solidification of any alloy depends on its chemistry that consequently affects the macro and microstructures for the given solidification conditions. In order to analyze the effects of chemistry on the release of latent heat during solidification of the industrial 3XX series of aluminum alloys, four different levels of silicon (5, 7, 9 and 11wt% Si) and three different levels of copper (1, 2 and 4 wt% of Cu) were taken into consideration. The solidification process was studied at cooling rates of 6 and 10°C/minute. The solidification path of these alloys was determined and the corresponding latent heat released during the solidification process was measured using a Differential Scanning Calorimeter (DSC). The tested hypoeutectic alloy chemical composition was expressed by the novel concept of silicon equivalency. The findings indicate that increases in the cooling rates shift the characteristic temperatures toward lower values without having a significant effect on the amount of released latent heat.

Abstract: In this work effect of cooling rate on the size of the grains, SDAS, β phases and thermal characteristic results of Al-Si cast alloys have been described. The solidification process was studied using the cooling and crystallization curve at cooling rate ranging from 0,1 °Cs-1 up to 1 °Cs-1. The main observation made from this work was that when cooling rate is increased the aluminum dendrites nucleation temperature and solid fraction at the dendrite coherency point increases, which implies that mass feeding is extended. In addition to that, it was observed that solidus temperature and size of the β phases decreases when cooling rate increases. Investigations were showed, that the thermal modification could be quantitatively assessed by analysis of the crystallization curve.