Mechanical Properties, Microstructural Features, and Correlations with Solidification Rates of Al–Cu–Si Ultrafine Eutectic Alloys

Abstract

Due to their optimized mechanical properties under rapid solidification, Al–Cu–Si ultrafine eutectic alloys have been highlighted. The literature does not, however, establish correlations between thermal solidification parameters, mechanical properties, and microstructures of these alloys. Knowledge of cooling rates and growth rates and their associations with mechanical properties of Al–Cu–Si ultrafine eutectic alloys can guide the search for controlled and optimized processing conditions. Considering these issues, the present study analyzes the correlations between microstructures and mechanical properties of Al–15 wt% Cu–7 wt% Si, Al–22 wt% Cu–7 wt% Si, and Al–26 wt% Cu–7 wt% Si alloys produced by centrifugal casting in a copper mold. For this, Al–Cu–Si alloys’ samples with a stepped solidified form are subjected to microstructural assessment and mechanical properties characterization methods. The results show the existence of phases such as Al‐rich, Si, and Al2Cu in different proportions for each cylindrical casting part. Eutectic bimodal structures have been observed. With the increase in either alloy Cu content or solidification cooling rate, increase in hardness is observed. However, the compressive strength is shown to be unaffected by the microstructural scale. These variations are discussed to guide the best balance of properties. Samples of the Al–26 wt% Cu–7 wt% Si alloy produced under eutectic growth rates between 0.8 and 1.2 mm s−1 are those with superior properties.