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

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.