Zn—Al合金热型连铸定向凝固的晶体生长机理

对热型连铸条件下Zn-Al系列合金引锭时的晶体形核和随后的本的竞争生长过程进行了探讨，组织观察表明，单向热流条件下引锭端部生核的晶粒当其枝晶择优生长方向与热流方向一致时才能生长，其它取向的晶粒逐渐被淘汰，合金的凝固特性对选晶过程有极大的影响，ZA5和ZA8合金由于凝固范围窄，晶体直接由引锭端部的晶粒通过竞争生长获得柱状晶组织，ZA12，ZA22和ZA27含Al量高，凝固范围宽，其平行柱状晶组织是从引锭端部的等轴晶区发展而来的。

CRYSTAL GROWTH MECHANISM OF DIRECTIONALLY SOLIDIFIED Zn-Al ALLOY IN CONTINUOUS CASTING BY HEATED MOLD

Nucleation and the competitive growth of grain in Zn-Al alloys during pulling ingot under the condition of continuous casting by heated mold were studied. The microstructure observation shows that nuclei appearing on the end of guide ingot have the orientation disorder during the competitive growth under the condition of directional heat flowing. Only when the growth direction of a dendritic crystal is the same as that of the heat flowing, can the crystal grow continuously, and the crystals with other directions will be gradually eliminated. The properties of alloy influence greatly the selecting process. The alloys with the narrow solidiflcation range, ZA5 and ZA8, can directly form columnar structure from nuclei on the end of the guide ingot through competitive growth. The alloys with higher aluminum amount, ZA12, ZA22 and ZA27, have wide solidification range, and their parallel columnar structure comes from developing of equiaxed crystal on the end of the guide ingot.