Understanding the mechanisms of degassing in heat-resistant Al–Si alloy: The synergistic effect of Si content and ultrasound

Ultrasonic treatment (UST) plays a crucial role in the degassing of heat-resistant aluminum alloy melts. This work investigates the effects of varying silicon (Si) contents in the alloy, UST power, and duration on the degassing efficiency of the melt. Experimental results indicate that both the Si content and the parameters of UST significantly influence the degassing performance of the alloy ingot. Specifically, with a UST power of 3000 W, a treatment duration of 100 s, and a Si content of 8 %, the density index of the alloy ingot reaches its lowest value of 0.32 %. Concurrently, the tensile strength and elongation achieve values of 264 MPa and 0.77 %, respectively. The degassing effects were further evaluated using a reduced pressure test (RPT) to examine the macroscopic pore structure of the ingot and by analyzing the section morphology under three-dimensional optical microscopy (OM-3D). Tensile testing was performed on samples subjected to varying UST durations, and the fracture surfaces of the tensile specimens were characterized. The phases surrounding the pores were identified using transmission electron microscopy (TEM), with particular attention paid to interactions between pores and inclusions. This study also provides an in-depth analysis of the ultrasonic cavitation mechanism, thereby offering valuable insights for future research on ultrasonic-assisted fluid purification and degassing processes.