脉冲电磁能对7A04铝合金凝固组织细化机理的影响
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摘要
在7A04铝合金凝固过程中施加脉冲电磁场,研究了脉冲电磁能对其凝固组织细化的影响,同时结合形核动力学进行了细化机理的研究。结果表明:在脉冲电磁能作用下,7A04铝合金可形成细小圆润的等轴晶,且细化程度与电磁能密度成正比。在频率为20 Hz时,磁能密度最大为2312 J/m~3,磁能渗入效果最佳,合金的平均晶粒尺寸减小30%。动力学分析认为,脉冲电磁能降低了体系形核所需的临界吉布斯自由能,形核率提升是合金晶粒细化的重要原因。
Pulse electromagnetic fields were applied to the solidification process of 7 A04 aluminum alloy, and effect of pulse electromagnetic energy on solidification microstructure refinement of the alloy was studied, and the refining mechanism was studied in combination with nucleation dynamics. The results show that the fine round equiaxed crystals can be formed in the 7 A04 aluminum alloy under the action of pulse electromagnetic energy, and the degree of refinement is proportional to the electromagnetic energy density. When the frequency is 20 Hz, the maximum magnetic energy density is 2312 J/m~3, and the magnetic energy penetration effect is the best, and the average grain size of the alloy decreases by 30%. The kinetic analysis shows that the pulse electromagnetic energy reduces the critical Gibbs free energy required for the nucleation of the system, and the increase of nucleation rate is an important reason for grain refinement of the alloy.
Pulse electromagnetic fields were applied to the solidification process of 7 A04 aluminum alloy, and effect of pulse electromagnetic energy on solidification microstructure refinement of the alloy was studied, and the refining mechanism was studied in combination with nucleation dynamics. The results show that the fine round equiaxed crystals can be formed in the 7 A04 aluminum alloy under the action of pulse electromagnetic energy, and the degree of refinement is proportional to the electromagnetic energy density. When the frequency is 20 Hz, the maximum magnetic energy density is 2312 J/m~3, and the magnetic energy penetration effect is the best, and the average grain size of the alloy decreases by 30%. The kinetic analysis shows that the pulse electromagnetic energy reduces the critical Gibbs free energy required for the nucleation of the system, and the increase of nucleation rate is an important reason for grain refinement of the alloy.
引文
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[14] 白庆伟,麻永林,邢淑清,等.铝合金表面脉冲电磁场对半连续铸造晶粒的细化[J].工程科学学报,2017,39(12):1828-1834.BAI Qing-wei,MA Yong-lin,XING Shu-qing,et al.Refining of a DC-casting aluminum alloy structure using surface electromagnetic pulsing[J].Journal of University of Science and Technology Beijing,2017,39(12):1828-1834.
[15] 胡谦谦,张立华.提高7050铝合金形核率的试验及理论分析[J].铸造,2011,60(12):1175-1179.HU Qian-qian,ZHANG Li-hua.Experimental and theoretical analysis on enhancing nucleation rate of 7050 aluminum alloy[J].China Foundry,2011,60(12):1175-1179.
[2] Vives C.Electromagnetic refining of aluminum alloys by the CREM process:Part I.Working principle and metallurgical results[J].Metallurgical Transactions B.1989,20(5):623-629.
[3] 金曼.电磁场作用下的7075铝合金凝固过程的研究[D]:沈阳:东北大学,2002.JIN Man.Study on solidification of 7075 Al alloy under electromagnetic fields[D].Shenyang:Northeastern University,2002.
[4] 訾炳涛,姚可夫,许光明,等.脉冲磁场下金属熔体凝固流场的数值模拟[J].物理学报,2003,52(1):115-119.ZI Bing-tao,YAO Ke-fu,XU Guang-ming,et al.Numerical simulation of liguid alloy flow field during solidification under applied pulsed magnetic fields[J].Acta Physica Sinica,2003,52(1):115-119.
[5] 张勤,崔建忠,路贵民,等.磁场强度对半连铸铝合金液穴形状及凝固组织的影响[J].金属学报,2002(9):956-960.ZHANG Qin,CUI Jian-zhong,LU Gui-min,et al,Effects of electromagnetic intensity on the sump shapes and structures of aluminum alloy produced by crem process[J].Acta Metallurgica Sinica,2002(9):956-960.
[6] 毕成,郭志鹏,LIOTTI E,等.铝合金凝固过程枝晶破碎现象的定量化研究[J].金属学报,2015,51(6):677-684.BI Cheng,GUO Zhi-peng,LIOTTI E,et al,Quantification study on dendrite fragmentation in solidification process of alluminum alloys[J].Acta Metallurgica Sinica,2015,51(6):677-684.
[7] 余建波,任忠鸣,任维丽,等.电磁振荡下梯度磁场对纯Al凝固组织的影响[J].金属学报,2007(11):1201-1206.YU Jian-bo,REN Zhong-ming,REN Wei-li,et al,Effects of gradient magnetic field on the solidification structure of aluminum under electromagnetic vibration[J].Acta Metallurgica Sinica,2007(11):1201-1206.
[8] 刘芳,张璐云.脉冲磁致振荡下纯铝凝固磁场与流场分布的数值模拟[J].铸造,2012,61(3):285-290.LIU fang,ZHANG Lu-yun.Numerical simulation of magnetic field and flow field distributions during pure aluminum solidification under pulse magneto-oscillation[J].China Foundry,2012,61(3):285-290.
[9] 班春燕.电磁场作用下铝合金凝固理论基础研究[D].沈阳:东北大学,2002.BAN Chun-yan.Fundamental study on solidification of Al alloys under electromagnetic fields[D].Shenyang:Northeastern University,2002.
[10] 王贵文.电磁场的特性初探[J].呼伦贝尔学院学报,2004,12(4):55-56.WANG Gui-wen.Preliminary study on the characteristics of electromagnetic field[J].Journal of Hulunbeir College,2004,12(4):55-56.
[11] 张玉民,戚伯云.电磁学.第2版[M].北京:科学出版社,2007.
[12] Bai Q,Ma Y,Xing S,et al.Nucleation and grain refinement of 7A04 aluminum alloy under a low-power electromagnetic pulse[J].Journal of Materials Engineering and Performance.2018,27(2):857-863.
[13] Bai Q,Ma Y,Xing S,et al.Effect of flow,heat transfer and magnetic energy on the grain refinement of 7A04 alloy under electromagnetic pulse[J].International Journal of Materials Research.2017,108(12):1-9.
[14] 白庆伟,麻永林,邢淑清,等.铝合金表面脉冲电磁场对半连续铸造晶粒的细化[J].工程科学学报,2017,39(12):1828-1834.BAI Qing-wei,MA Yong-lin,XING Shu-qing,et al.Refining of a DC-casting aluminum alloy structure using surface electromagnetic pulsing[J].Journal of University of Science and Technology Beijing,2017,39(12):1828-1834.
[15] 胡谦谦,张立华.提高7050铝合金形核率的试验及理论分析[J].铸造,2011,60(12):1175-1179.HU Qian-qian,ZHANG Li-hua.Experimental and theoretical analysis on enhancing nucleation rate of 7050 aluminum alloy[J].China Foundry,2011,60(12):1175-1179.