Effect of melt cooling rate on the microstructure and thermal properties of Al – Ge alloy

Abstract

The paper presents the results of comparing the microstructure of alloys of the Al – Ge system of eutectic and near- eutectic compositions synthesized at melt cooling rates of 102 and 105 K/s. It was shown by scanning electron microscopy that at a cooling rate of 102 K/s, crystallization starts with grain growth of the excess component and ends with a eutectic reaction. The microstructure of bulk samples is characterized by large inclusions of aluminum and germanium and heterogeneity of composition at sample cross section. The size reduction of phase particles of alloys of the Al – Ge system of eutectic and near-eutectic compositions is achieved using high-speed solidification. It is shown that the cooling rate of the melt increase causes size reduction of phase particles by 2–3 orders. The layering of the microstructure of the cross section of rapidly solidified foils was also revealed, and a mechanism for its formation was proposed taking into account changes in the solidification conditions over the thickness of the foil. Using differential scanning calorimetry, it was shown that an increase in the cooling rate provides a narrowing of the melting temperature range and an increase in the melting rate.