Influence of ultrasonic treatment on formation of primary Al3Zr in Al-0.4Zr alloy
(1. Brunel Centre for Advanced Solidification Technology, Brunel University London, Uxbridge, London, UB8 3PH, UK;
2. Tomsk State University, Tomsk 634050, Russia;
3. Diamond Light Source Ltd., Harwell Science & Innovation Campus, Didcot, OX11 0DE, UK;
4. School of Engineering, University of Hull, Hull, East Yorkshire, HU6 7RX, UK)
2. Tomsk State University, Tomsk 634050, Russia;
3. Diamond Light Source Ltd., Harwell Science & Innovation Campus, Didcot, OX11 0DE, UK;
4. School of Engineering, University of Hull, Hull, East Yorkshire, HU6 7RX, UK)
Abstract: The effect of ultrasonic treatment on the formation of primary Al3Zr was investigated by applying ultrasound to an Al-0.4Zr alloy. Three temperature ranges were selected, i.e., 830 to 790 °C (above liquidus), 790 to 750 °C (cross liquidus) and 750 to 710 °C (below liquidus) for ultrasonication. Using the scanning electron microscopy, both the size and morphology of the primary Al3Zr particles were examined. It was found that the size was significantly reduced and the morphology changed from large throwing-star shape to small compact tablet shape. The mechanisms for refinement of primary Al3Zr were discussed. It is suggested that sonocrystallization theory via activation of aluminium oxide particles is responsible for the refinement of primary Al3Zr when ultrasonic melt treatment (UST) is applied within the fully liquid state. The refinement of primary Al3Zr particles when UST is applied in the slurry (growth stage) is due to the sonofragmentation.
Key words: ultrasonic treatment; aluminium alloy; primary Al3Zr intermetallic; refinement; crystal morphology