Importance of Melt Cleaning Parameters on Reliability of Tensile Properties in A356 Alloy

This study examines how melt treatment and pouring temperature affect the microstructure and mechanical properties of A356 aluminum alloy. Samples were cast under degassed, non-degassed, and upgassed conditions at 725, 750, and 775 °C. Melt quality was assessed using the reduced pressure test (RPT) and the bifilm index (BI), while microstructural features were analyzed via SEM and EDS. Tensile testing and Weibull statistics were used to evaluate mechanical performance and variability. Results showed that by improper degassing the reproducibility of mechanical properties decreased regardless of hydrogen content of the melt. When bifilm index (BI) was high (> 50 mm), the ductility was lowered and caused greater variability in strength and elongation. SEM confirmed large oxide films in samples, linked to the brittle fracture. The work also highlighted the importance of melt cleaning parameters for the reliability of cast aluminum alloys regardless of the hydrogen content.