New Trends in Aluminium Degassing –A Comparative Study

This work aims to evaluate the efficiency of ultrasonic degassing when applied to the AlSi9Cu3 alloy when compared with other degassing techniques. The mechanism of aluminium degassing is discussed. A suitable ultrasonic degassing apparatus including a novel MMM (Multi-frequency Multimode Modulated) technology, able to supply up to 1.2 kW power under a frequency up to 25 kHz, was developed specially for this purpose. Ultrasonic degassing is compared with rotary impeller degassing using argon and nitrogen as purging gases. Results characterization focuses the assessment of alloy density and final hydrogen content of the samples, using the Straube-Pffeifer method. Experimental results reveal that a constant value of density and hydrogen content can be reached after less than 2 minutes processing time, using ultrasonic energy, which is 3 times faster than rotary impeller degassing. Regardless of the processing time, final results (density and hydrogen concentration) achieved with ultrasonic degassing are much better than those reached using the gas purging technique.