高合金化大規格構件錠坯過飽和凝固成形與性能的外場調控研究

李曉謙

摘要：針對大型整體構件坯料厚度增大到600mm以上，溫度場嚴重不均勻造成合金成分不均，宏微觀偏析嚴重，晶粒粗大，疏松嚴重，易形成粗大的未溶相組織。針對以上問題，發展新原理，減小溫度場和組織不均勻性，克服宏微偏析，取得以下成就： 1、首次發現并探索了超聲外場作用下的結晶體共振現象與機理，并從動力學角度分析了共振效應對晶粒細化的影響，系統研究了超聲場對鋁合金凝固的各種作用機理。2、針對超聲場對鋁合金熔體異質形核作用及熔體微細質點的活化作用與活化機理進行了深入研究，建立了超聲場作用下鋁合金凝固過程動力學模型。3、分析了超聲場作用下熔體過冷度、合金元素固溶度、液固界面的傳熱、傳質行為特征。4、完成了多組平面復合行波磁場協同電磁鑄造系統的設計及實驗調試。5、成功進行了7050鋁合金圓錠與扁錠超聲外場輔助鑄造工藝實驗。

關鍵詞：超聲鑄造；凝固成形；偏析

Abstract：When the billet thickness of large size component increase to more than 600 mm， Al-alloy composition will become inhomogeneous， produce macro and micro segregation seriously， grains will become coarse and loose， and it is easy to form a coarse undissolved phase because of the serious uneven temperature field. To solve these problems， Efforts have made to develop new principles， to reduce the Inhomogeneity of the temperature field and tissue， to overcome the macro and micro segregation， and the following achievements have made ： 1. For the first time revealed the phenomenon and mechanism of crystal resonance under the effect of ultrasonic outfield， analyzed the effect of resonance on grain refinement from the point of dynamics， systematically studied various mechanisms of effects of ultrasonic outfield on the solidification of Al alloys. 2. Further investigated the activation effect and mechanism of ultrasonic field on heterogeneous nucleation and fine particles of Al alloys melts， established the dynamic model of solidification process of Al alloys under ultrasonic outfield. 3. Analyzed the properties of melts under ultrasonic outfield， including the degree of supercoiling， solid solubility of elements， heat and mass transport properties of liquid-solid interface. 4.We have completed the design and experimental testing of multiple plane complex traveling magnetic field collaborated with electromagnetic casting system . 5.We have successfully conducted the 7050 aluminum alloy ingot and flat ingot ultrasonic assisted casting process outfield experiment， obtained ingot grain size of 72-118μm， flat ingot grain size of 151-245μm .

Keywords：Ultrasonic casting； solidification；Segregation