This work focuses on ultrasonic melt treatment (UST) in a launder upon pilot-scale direct chill (DC) casting of 152-mm-diameter billets from an AA6XXX alloy with Zr addition. Two casting temperatures (650°C and 665°C) were used to assess their effect on the resulting microstructure (grain size, particle size, and number density). Structure refinement results show the feasibility of UST in the DC casting launder. This is quantified through the corresponding reduction of grain size by around 50% in the billet center, or more towards the billet surface, reduction of the average Al3Zr particle size, and increase in the particle number density. A higher Al3Zr particle density was obtained when the alloy was cast at 665°C. Numerical simulation results and suggestions on how to improve the treatment quality of UST in DC casting launder are also provided.

中文翻译：

---

直流铸造流槽中超声波熔体处理的结构细化

这项工作的重点是在使用添加 Zr 的 AA6XXX 合金对直径 152 毫米的钢坯进行中试规模的直冷 (DC) 铸造时，在流槽中进行超声波熔体处理 (UST)。使用两种铸造温度（650°C 和 665°C）来评估它们对所得微观结构（晶粒尺寸、颗粒尺寸和数量密度）的影响。结构细化结果表明 UST 在直流铸造流槽中的可行性。这是通过钢坯中心晶粒尺寸相应减少约 50%，或更多朝向钢坯表面、平均 Al3Zr 粒径减小和颗粒数密度增加来量化的。当合金在 665°C 下铸造时，获得了更高的 Al3Zr 颗粒密度。还给出了如何提高直流浇铸流槽中UST处理质量的数值模拟结果和建议。