Features of structure formation and thermal expansion of high alloys of the Al–Si–Cu system

Abstract

The study results of the copper alloying effect on the microstructure and thermal coefficient of linear expansion (TCLE) of high aluminum alloys for special purposes based on the Al – (20÷30)% Si system are presented. It was found that alloy building of Al – 20% Si with copper in large quantities eliminates the linear expansion anomaly characteristic to the binary alloy and leads to a significant decrease in the thermal expansion coefficient over the entire temperature range of the tests. It was shown that Al–30%Si–20÷40% Cu alloys have stable TCLE in the low-temperature test interval. Metallographic analysis of high alloys showed that copper introduced in amounts of more than 20% contributes to a change in the morphology of the silicon phase and triple eutectic.

Effect of CuAl2 on the Microstructure and Hardness of Al-Si-xCu Alloys Produced by Powder Metallurgy

“…With the addition of copper atoms and sintering temperature, the diffusion of copper atoms increased as the copper atoms concentration increased. This diffusion increases the aluminum dendrite arms, especially the secondary dendrite arms (SDA) [26], as shown in Figure . (6a). In addition, the dendritic nature of the aluminum particles is very clear, as can be seen from the image in Figure . (6b), which was processed and modified using ImageJ software.…”

“…The influence of the Cu-content on the internal structure of the compacted alloys is also observed in the same Figures. Based on a previous study [26] and Figure . (5), it can be observed that the microstructure of the Al-Si alloy consists of primary crystalline silicon and an Al-Si eutectic phase surrounded by a dendritic primary α-Al phase with a higher size and volume fraction. The silicon particles were found to be spherical and flower-shaped, as shown in Figure . (5a).…”