高合金化大规格构件锭坯过饱和凝固成形与性能的外场调控研究

李晓谦

摘要：针对大型整体构件坯料厚度增大到600mm以上，温度场严重不均匀造成合金成分不均，宏微观偏析严重，晶粒粗大，疏松严重，易形成粗大的未溶相组织。针对以上问题，发展新原理，减小温度场和组织不均匀性，克服宏微偏析，取得以下成就： 1、首次发现并探索了超声外场作用下的结晶体共振现象与机理，并从动力学角度分析了共振效应对晶粒细化的影响，系统研究了超声场对铝合金凝固的各种作用机理。2、针对超声场对铝合金熔体异质形核作用及熔体微细质点的活化作用与活化机理进行了深入研究，建立了超声场作用下铝合金凝固过程动力学模型。3、分析了超声场作用下熔体过冷度、合金元素固溶度、液固界面的传热、传质行为特征。4、完成了多组平面复合行波磁场协同电磁铸造系统的设计及实验调试。5、成功进行了7050铝合金圆锭与扁锭超声外场辅助铸造工艺实验。

关键词：超声铸造；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