Zn对Al-Zn-Mg-Cu铸轧板组织和裂纹影响

Effects of Zn content on the microstructure and cracks during twin-roll casting of Al-Zn-Mg-Cu cast-rolled strips

摘要:

本文研究了五种不同Zn含量的铸轧Al-Zn-Mg-Cu合金（3.5 wt %，5 wt %，6.5 wt %，8 wt %和10 wt %，分别标记为Zn3.5，Zn5，Zn6.5，Zn8和Zn10）的宏观裂纹和微观组织。研究结果表明，Zn含量由10 wt %减少至5 wt %时，铸轧条带的宏观裂纹数量明显降低；但当Zn含量由5 wt %减少至3.5 wt %时，裂纹数量减少十分有限。铸轧条带显微组织从表层到中心呈柱状晶向等轴晶的转变。随着Zn含量的增加，铸轧板中心低熔点共晶相偏聚带变宽，粗大非平衡共晶相数量增多，偏析加重。在高Zn含量（10 wt %）的铸轧条带组织中有明显的孔洞存在。

Abstract:

The microstructure and macroscopic cracks of five twin-roll cast Al-Zn-Mg-Cu alloys strips with various Zn contents (3.5 wt pct, 5 wt pct, 6.5 wt pct, 8wt pct, and 10 wt pct, marked as Zn3.5, Zn5, Zn6.5, Zn8, and Zn10, respectively) were investigated. The results showed that the macroscopic cracks of strips decreased in numbers as the Zn content decreased from 10 wt pct to 5 wt pct, while this decrease was inhibited as the Zn content continuously decreased from 5 wt pct to 3.5 wt pct. The microstructure sustained a transition from columnar crystals to equiaxed crystals along the surface to the center of the cast strip. The center segregation band of the cast strips became wider and the non-equilibrium coarse eutectic phases increased in amount as the Zn content increased in these Al-Zn-Mg-Cu strips. Unsolidified liquid phases and holes appeared in the microstructures of strips of high Zn content.