超声场作用下7050铝合金的溶质再分配与组织形成的建模仿真与分析

Growth suppression effects of alloy composition on 7050 aluminum alloy melt treated by ultrasonic

对不施加超声、施加300 W、1 000 W功率超声处理的半连铸成形7050铝合金大扁锭进行晶粒细化的实验研究,并基于元胞自动机-有限元(CAFE)法,建立7050铝合金形核和晶粒生长的数学模型,得到形核参数对仿真结果的作用规律。依靠成分过冷发展的初始阶段建立生长限制因数Q的物理模型,对超声细化晶粒的机制进行说明。模拟和实验结果表明:1 000 W功率超声的晶粒细化效果最佳,此时晶粒的平均尺寸为204μm;模具表面形核的高斯分布平均过冷度、模具表面以及熔体内部形核的高斯分布标准方差对预测晶粒结构影响不大,模具表面及熔体内部形核的高斯分布最大形核密度、熔体内部形核的高斯分布平均过冷度对仿真结果影响显著;晶粒尺寸随Q值增大呈大致单调递减趋势,晶粒大小与Q具有良好的关联性。

The experiments of power ultrasound on grain refinement of aluminum alloy 7050 large billets prepared by applying ultrasonic field and conventional semi-continuous casting were investigated. Based on the process of coupling cellular automation with finite elements, the mathematical models of nucleation and grain growth of 7050 aluminum alloy were established, and the nucleation parameters on the influence of the simulation results were established. A comprehensive physical basis of Q was obtained by using the initial rate of development of constitutional supercooling to illustrate the mechanism of grain refinement by ultrasonic. The simulation and experimental results show that grain refinement effect with 1 000 W power ultrasonic is the best, and the average grain size is 204 pro. The mean undercooling of nuclei at the surface of mold and the standard deviation of nuclei at the surface and in the bullk liquid, have little effect on the simulation results. On the contrary, the maximum density of nuclei at the surface and in the bullk liquid and the mean undercooling of nuclei in the bullk liquid, have significant effects. Grain sizes are roughly in the monotone decreasing trend with the increase of Q, and Q possesses good correlation with the grain sizes.