The potential for producing a large refined equiaxed zone by ultrasonic treatment (UST) of high purity zinc was investigated in order to improve the mechanical performance and formability. The macrostructure of cast ingots changed from large columnar grains without UST to three zones of fine columnar grains adjacent to the mould walls of the ingot, a refined equiaxed zone and a zone of a mixture of coarse equiaxed and columnar grains. A small zone of equiaxed grains was obtained when UST was applied during cooling from 440 °C to 419 °C for 2 min. The size of the equiaxed zone increased from about 20% of the casting's cross section to 50% when UST was applied for 3 or 4 min. In contrast, the application of UST for a longer time from a higher temperature (450–419 °C for 4 min) resulted in a smaller equiaxed zone of 18% indicating that a specific combination of UST time and temperature is required for the formation of a large equiaxed zone. The factors affecting the formation of the equiaxed zone throughout the solidification cycle are described.

中文翻译：

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超声波处理对铸态高纯锌晶粒形成机制的影响

研究了通过超声处理 (UST) 对高纯锌产生大的精炼等轴区的潜力，以提高机械性能和成型性。铸锭的宏观组织从没有 UST 的大柱状晶转变为三个与铸锭结晶器壁相邻的细柱状晶区、一个细化等轴区和一个粗等轴和柱状晶混合区。当在从 440°C 冷却到 419°C 2 分钟期间应用 UST 时，获得了一小块等轴晶粒区域。当 UST 施加 3 或 4 分钟时，等轴区​​的尺寸从铸件横截面的约 20% 增加到 50%。相比之下，从更高的温度（450-419°C 持续 4 分钟）应用更长时间的 UST 导致 18% 的较小等轴区，表明 UST 时间和温度的特定组合需要形成大的等轴区区。描述了在整个凝固循环中影响等轴区形成的因素。