【摘要】 一体化压铸成形技术的发展要求免热处理的铝合金材料具有高的强韧性，然而在成形过程中，大型压铸件会存在预结晶组织(ESC)及孔洞等缺陷，导致其使役性能降低.在压铸过程中，真空度越低，液流充型过程中因卷气所带来的气孔含量越高；而预结晶组织含量越高，在铸件心部越容易产生ESC枝晶网络，大尺寸缩松的含量也因此提高.虽然增加抽真空时间能够提高真空效果，但熔体在压室中长时间停留会增大ESC含量.本研究中通过设计流道的方式来调控充型过程中液体的运动速度，达到破碎分散ESC的目的，减少或避免在铸件中形成大尺寸ESC枝晶网络，降低铸件中的孔隙率.结果表明：在弯折浇道配合的高真空压铸工艺下，ESC实现了均匀分布，试棒中的孔隙率大幅度降低，大尺寸孔洞被消除.该研究结果可为调控压铸件大尺寸ESC和孔洞提供新的思路.更多还原

【Abstract】 The development of integrated die-casting forming technology requires aluminum alloy materials without heat treatment to have high strength and toughness. However, large die-casting parts are prone to defects such as externally solidified crystal(ESC) and pores during the forming process, which reduces the service performance of the castings. In the process of vacuum die casting, the lower the vacuum degree leads to the higher porosity during the high-speed liquid filling. In addition, the higher the ESC content is, the more ESC dendrite network is easily formed in the center of the casting which is closely associated with the formation of large-sized shrinkage. Increasing the vacuum pumping time can improve the vacuum effect while prolonging the residence of the melt in the shot sleeve, which forms more ESC at the same time. In this study, the runner is designed to regulate the filling speed of liquid during the die casting process, to achieve the purpose of breaking and dispersing ESC, reduce or avoid the formation of large ESC dendrite network, and reduce the porosity in the casting. The results indicate that under the high vacuum die-casting process with bent runner matching, ESC achieves uniform distribution, which significantly reduces porosity and eliminates large-sized pores. This research result provides a new idea for regulating large-sized ESC and pores in die-casting parts.更多还原