直流电流密度对Al-5Cu合金凝固组织的影响

Effect of Direct Current Density on Solidification Microstructure of Al-5Cu Alloy

本文通过在石膏型铸造中施加不同电流密度的直流电场,研究电流密度对Al-5Cu合金凝固组织的影响规律。当电流密度从0 mA/mm^(2)增大到25 mA/mm^(2)时,α-Al晶粒尺寸逐渐减小,位于正极附近的柱状晶长度随电流密度的增加而逐渐变长,而负极附近柱状晶长度的变化与正区柱状晶长度的变化相反。当电流密度大于25 mA/mm^(2)时,α-Al晶粒尺寸逐渐增大,正极附近柱状晶粒长度减小,但是负极柱状晶变化不大。通过Al-5Cu合金凝固过程冷却曲线,分析电流密度对过冷度的影响,并从形核和长大的角度讨论了直流电对晶粒形貌和尺寸的影响机理,揭示了珀耳帖效应和焦耳效应对Al-5Cu合金凝固组织的影响规律。

The effect of current density on the solidification structure of Al-5Cu alloy was studied by applying direct current electric field with different current density in gypsum mold casting.It was found that during solidification,the grain size first decreased and then increased,the length of columnar crystal near the positive electrode first increased and then decreased,the current density increased from 0 mA/mm^(2)to 25 mA/mm^(2),the grain size ofα-Al decreased gradually,the length of columnar grain near the positive electrode increased;while the current density was greater than 25 mA/mm^(2),the grain size ofα-Al increased gradually,the length of columnar grain near the positive electrode decreased gradually,however the columnar crystal near negative electrode had change a little.The change of columnar crystal length in the negative region was opposite to that in the positive region.The influence of direct current on undercooling was analyzed.Based on the theory of nucleation and grain growth,the effect mechanism of direct current on grain morphology and size was discussed,and the effects of Peltier effect and Joule effect on the solidification structure of Al-5Cu alloy were clarified.