中文摘要：

在超声处理铝硅合金的过程中，伴随着金属液的凝固，一部分半固态金属会在超声工具头附近溢出并沿工具头向上爬升。研究超声处理过程中的这种特殊现象，并对其成因及溢出部分的微观组织变化进行讨论。结果表明：溢出现象与半固态金属中的液体流动和振动模式变化有关。溢出部分来自于超声作用最强烈的区域，且在凝固过程中随超声工具头进行高频振动，因此在溢出部分得到十分细化的凝固组织。初生α（Al）由粗大的树枝晶变为细小的等轴晶，尺寸减小为约70μm；块状初生硅和针片状共晶硅全部变为细小的硅晶粒，尺寸减小至约10μm。

英文摘要：

At the late stage of solidification with ultrasonic treatment （UST） in Al-Si alloys, a part of semisolid overflows and climbs along the probe. The interesting phenomenon and its influence on the solidification microstructure were investigated in order to better study the mechanism of UST. It is considered that the overflowing phenomenon occurs due to the changes of vibration and flow in the remaining semisolid. Because the overflowed portion comes from the region with intense UST effect and vibrates with the probe during solidification, great modification of primary and euteetic Si （about 10 pm in length） and refinement of primary a（Al） （about 70 μm in size） are observed in this portion.