Purification And Undercooling Of Al-4% Cu Eutectic Alloy Solidification

High undercooling of melts can result in rapid solidification of melts at low cooling rates. Therefore, this technique has been widely used in fundamental research of rapid solidification. The fundamental technique and engineering controlling condition for Al-4%Cu alloy to obtain high undercooling was systematically investigated. It was found that high undercooling could be obtained by superheating and denucleating with chloride flux under the protection of Argon.Based upon this, the exploring research work in microstructure of Al-4%Cu alloy have been researched, the influence of melt superheat treatment(including superheating temperature ,superheating time) on the solidification microstructure and the primary dendrite arm spacing of directionally solidified Al-4%Cu alloy was studied. We discussed the mechanism of the influence of melt superheat treatment on solidification structure, property and crystal orientation in order to enrich solidification theory and instruct practice. The main results and contributions of the paper are as follows:(1) By the method of superheating and denucleating with chloride flux under theprotection of Argon, a high undercooling up to 70K has been obtained in Al-4%Cu alloy. The results show that the sticky flux can get effectively rid of the heterogeneous nucleuses in the mett and make the alloy obtain lower undercooling.(2) It is found that the cycle number, temperature and denucleating time can puteffect on the undercooling of melt; The undercooling of Al-4%Cu alloy melt will increase with increasing the superheating of melt, however, when the superheating exceeds a limitation, the undercooling will decreased; with the increasing of denucleating time, the denucleating effect will increase obviously at initial staves, then the undercooling keeps almost unchanged; the undercooling of Al-4%Cu alloy will increase with the increase of cycle number, and increase to maximum at the 4 to 5 cycle, henceforth tend to a constant state.(3) The melt superheat temperature can influence the directionally solidified...