超声诱致的温度波动对铝合金熔体过冷形核的影响  

Effect of Temperature Fluctuation Induced by Ultrasonic on Undercooling Nucleation in Aluminum Alloy Melt

作　　者：宁佳杰 李晓谦[1] 李瑞卿[1] 黄明哲[1] 

机构地区：[1]中南大学机电工程学院高性能复杂制造国家重点实验室

出　　处：《特种铸造及有色合金》2014年第2期208-212,共5页Special Casting & Nonferrous Alloys

基　　金：国家重点基础研究发展计划(973计划)资助项目(2010CB731706;2012CB619504)

摘　　要：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 imposed on 7085 aluminum alloy melt during solidification to measure the temperature change in the melt caused by ultrasonic,and the temperature fluctuation in the melt occurs.Effects of the temperature fluctuation on undercooling nucleation in the aluminum alloy melt were investigated.The results show that cavitation bubbles caused by ultrasonic absorb heat during growth process to decrease the temperature around cavitation bubbles,while heat is released to increase the temperature around when cavitation bubbles collapse.In the experiment,the amplitude of temperature fluctuation is in range of 2～6℃,leading to the initial nucleation temperature increased from 638.4 ℃ to 644.5 ℃.Within the undercooling nucleation region,the temperature fluctuation can enhance the local undercooling degree and increases the maximum nucleation density from 47.1/mm3 to 92.6mm3.In the process of dendrite growth,the temperature fluctuation makes the necking-down dendrite side arm easier to detach,which increases new nucleus in the melt.

关 键 词：超声 温度波动 过冷度 形核 

分 类 号：TG292[金属学及工艺—铸造]