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在7085铝合金凝固过程中施加超声,测量超声作用引起熔体温度的变化,发现施加超声后熔体产生小幅温度波动,研究了该温度波动对铝合金熔体过冷形核的影响。结果表明,超声作用产生的空化泡在增大过程中吸收热量,使得周围熔体温度下降,而空化泡崩溃时释放热量,提高周围熔体温度;试验中超声空化引起的温度升高与降低在熔体局部温度波动值为2～6℃;局部温度波动使熔体形核起始温度从638.4℃提高至644.5℃;熔体过冷形核时,温度的向下波动能增大熔体局部过冷度,使局部熔体最大形核密度由47.1mm-3提高至92.6mm-3;在枝晶生长过程中,温度波动使颈缩的枝晶二次臂更容易熔断,在熔体中增加新的晶核。
Ultrasonic was applied during the solidification of 7085 aluminum alloy to measure the change of the melt temperature by the ultrasonic action. It was found that the melt produced slight temperature fluctuation after the ultrasonic was applied. The effect of this temperature fluctuation on the nucleation of the aluminum alloy melt was studied. The results show that the cavitation bubbles generated by the ultrasonic action absorb heat in the process of increasing, and the temperature of the surrounding melt decreases, while the cavitation bubbles collapse to release heat and increase the temperature of the surrounding melt. In the experiment, the temperature caused by ultrasonic cavitation increases And lower the local temperature fluctuations in the melt value of 2 ~ 6 ℃; local temperature fluctuations make the melt nucleation start temperature increased from 638.4 ℃ to 644.5 ℃; melt undercooled nucleation, the temperature fluctuation can increase The local undercooling of the melt increased the maximum nucleation density of the local melt from 47.1 mm-3 to 92.6 mm-3. During the growth of dendrites, the temperature fluctuated so that the necked dendrite secondary arm could be fussed more easily. Add new nuclei to the melt.