The Effect of Casting Speed and the Fraction of Al5%Ti1%B Inoculant on the Microstructure and Mechanical Properties of the AA5052 Aluminum Alloy Produced by the Direct Chill Process

This study aimed to assess the effect of casting speed and the addition of Al5%Ti1%B inoculant in the casted AA5052 aluminum alloy plate manufactured by the Direct Chill process. The focus of this work was to decrease the rejection index of rolled products due to the occurrence of superficial flaws on plates. These defects impact directly on the production costs and on the rolled product quality. The main cause of those flaws is associated with the billet porosity that is related with the excess of atomic hydrogen incorporated into the metallic bath and with the metal shrinkage during solidification. Four different cast conditions were industrially tested, combining two casting speeds and two inoculants amounts. The effect of those variables on the alloy mechanical properties and on their performance in rolling process was also assessed. It was observed that the higher the casting speed and the inoculant fraction, the more refined the microstructure and the lower the fraction and diameter of formed micropores. The increase of casting speed and the inoculant fraction improved the AA5052 alloy rolling performance. The application of these results in an industrial scale performed a decrease from 5.03% to 0.39% per month in the rejection index of rolled products.

本研究旨在评估铸造速度与Al-5%Ti-1%B变质剂（Al5%Ti1%B inoculant）的添加量，对采用直接冷铸工艺（Direct Chill process）制备的AA5052铝合金（AA5052 aluminum alloy）铸板的影响。本研究的核心目标是降低因铸板表面缺陷引发的轧制产品废品率（rejection index），此类缺陷直接影响生产成本与轧制产品质量，其主要成因与铸坯孔隙率相关：铸坯孔隙率与溶解于金属熔池的过量原子氢以及凝固过程中的金属收缩密切关联。本研究在工业场景下测试了四种不同的铸造工况，组合了两种铸造速度与两种变质剂添加量，同时评估了上述变量对合金力学性能及轧制性能的影响。研究观察到，铸造速度与变质剂添加比例越高，合金微观组织越细化，生成的微孔（micropores）占比与孔径均越低。提升铸造速度与变质剂添加比例可改善AA5052铝合金的轧制性能。将该研究成果应用于工业生产后，轧制产品的月度废品率从5.03%降至0.39%。