Zhou Li, Luo Yajun, Zhang Zhenlin, He Min, Xu Yinao, Zhao Yulei, Liu Sheng, Dong Lijun, Zhang Zhifeng
Hunan Engineering Research Center of New Energy Vehicle Lightweight, Hunan Institute of Engineering, Xiangtan 411104, China.
Wenchang New Material Technology Co. Ltd., Loudi 417000, China.
Materials (Basel). 2021 Feb 3;14(4):708. doi: 10.3390/ma14040708.
In this study, large-sized Al-Zn-Mg-Cu alloy billets were prepared by direct chill casting imposed with annular electromagnetic stirring and intercooling; a process named uniform direct chill casting. The effects of uniform direct chill casting on grain size and the alloying element distribution of the billets were investigated and compared with those of the normal direct chill casting method. The results show that the microstructures were refined and the homogeneity of the alloying elements distribution was greatly improved by imposing the annular electromagnetic stirring and intercooling. In uniform direct chill casting, explosive nucleation can be triggered, originating from the mold wall and dendrite fragments for grain refinement. The effects of electromagnetic stirring on macrosegregation are discussed with consideration of the centrifugal force that drives the movement of melt from the central part towards the upper-periphery part, which could suppress the macrosegregation of alloying elements. The refined grain can reduce the permeability of the melt in the mushy zone that can restrain macrosegregation.
在本研究中，通过施加环形电磁搅拌和间接冷却的直接水冷铸造制备了大型Al-Zn-Mg-Cu合金铸坯；该工艺称为均匀直接水冷铸造。研究了均匀直接水冷铸造对铸坯晶粒尺寸和合金元素分布的影响，并与常规直接水冷铸造方法进行了比较。结果表明，通过施加环形电磁搅拌和间接冷却，微观组织得到细化，合金元素分布的均匀性得到显著改善。在均匀直接水冷铸造中，可触发爆发形核，其源于铸模壁和枝晶碎片，用于细化晶粒。考虑驱动熔体从中心部位向上周边部位移动的离心力，讨论了电磁搅拌对宏观偏析的影响，该离心力可抑制合金元素的宏观偏析。细化的晶粒可降低糊状区熔体的渗透率，从而抑制宏观偏析。
