ABSTRACT

The productivity and recovery of hot-rolled Al-Mg-Mn sheets often suffer from sodium-induced edge cracking. In this study, AA5182 ingots with different levels of Na were prepared by direct-chill (DC) casting, and were then subsequently subjected to homogenisation and hot-rolling processes. The edge crack occurrence during hot rolling in the pass #11 (84% reduction) and pass #18 (96% reduction) was investigated, with special attention paid to the impact of intermetallic constituents in the ingot subsurface region, where all edge cracks were initiated. Correlations between the susceptibility to edge cracking, enriched intermetallic constituents in the inverse segregation zone, Mg₂Si cavitation, meniscus bands, and Na contamination were observed. The results revealed that Fe-rich intermetallic particles were not involved in crack formation, while Mg₂Si particles had a strong tendency to debond from the Al matrix and form cavities at the edges of the rolled strip. The higher the Na content, the more severe the Mg₂Si cavitation, and consequently, the higher the susceptibility to edge cracking. Numerous debonded Mg₂Si particles contaminated with Na in the subsurface region provided favourable conditions for crack initiation and propagation. The role of the meniscus bands on the large and profound edge cracks was also elaborated.

摘要

热轧 Al-Mg-Mn 板的生产率和回收率经常受到钠致边裂的影响。在这项研究中，具有不同 Na 含量的 AA5182 锭通过直冷 (DC) 铸造制备，然后进行均质化和热轧工艺。研究了 11 号道次（84% 压下率）和 18 号道次（96% 压下率）热轧过程中边缘裂纹的发生，特别注意了铸锭亚表面区域金属间成分的影响，其中所有边缘裂纹都在发起。边缘裂纹敏感性与逆偏析区富集金属间化合物 Mg ₂之间的相关性观察到 Si 空化、弯液面带和 Na 污染。结果表明，富铁金属间化合物颗粒不参与裂纹的形成，而 Mg ₂ Si 颗粒有很强的从铝基体剥离的趋势，并在轧制带材的边缘形成空腔。Na含量越高，Mg ₂ Si空化越严重，因此对边缘裂纹的敏感性越高。地下区域中被 Na 污染的许多脱粘的 Mg ₂ Si 颗粒为裂纹萌生和扩展提供了有利条件。还详细阐述了弯月带对大而深的边缘裂纹的作用。