交变磁场-压力协同场对真空差压铸造ZL114A合金枝晶生长及致密度的影响  

Effects of Alternating Magnetic Field and Pressure Co-field on Dendrite Growth and Density in Vacuum Differential Pressure Casting ZL114A Alloy

作　　者：李勇 严青松 芦刚 陈燕飞 陈义斯 朱伟明 刘栋 Li Yong;Yan Qingsong;Lu Gang;Chen Yanfei;Chen Yisi;Zhu Weiming;Liu Dong(National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology,Nanchang Hangkong University;Jiangxi Hongdu International Mechanical&Electrical Co.,Ltd.)

机构地区：[1]南昌航空大学轻合金加工科学与技术国防重点学科实验室,南昌330063 [2]江西洪都国际机电有限责任公司

出　　处：《特种铸造及有色合金》2023年第6期808-814,共7页Special Casting & Nonferrous Alloys

基　　金：国家自然科学基金资助项目(51861027);南昌航空大学博士启动基金资助项目(EA202203058)。

摘　　要：为强化复杂薄壁铝合金凝固末期补缩,获得高致密ZL114A铝合金铸件,在真空差压铸造机上构建磁场发生装置。系统研究了磁感应强度和分级加压压差对不同轴径ZL114A试样枝晶形态、取向、二次枝晶间距(SDAS)、致密度的影响,揭示了交变磁场-压力协同场下合金的凝固行为,建立了交变磁场-压力协同场下熔体对流挤渗方程。结果表明,协同场下的熔体质点受洛伦兹力和压力影响持续运动,并伴随初生枝晶碎断、浮游、二次生长及变形,故凝固组织趋于等轴化,粗大树枝晶转变为细小蔷薇晶。此外,XRD图谱显示主晶面(111)衍射峰强度随磁感应强度增加而增加,证实交变磁场促进低阶晶面枝晶择优生长。强磁场下金属原子运动剧烈,引起熔体过热影响凝固进而导致组织粗化。因此,随着磁感应强度增加,合金SDAS(二次枝晶臂间距)先减小后增大,致密度先增大后减小,理想磁场强度为24 mT,此时提高分级加压压差有利于枝晶细化和凝固补缩。In order to strengthen the feeding of complex thin-wall aluminum alloy at the end of solidification and obtain high-density ZL114A aluminum alloy castings,a magnetic field generator was constructed on a vacuum differential pressure casting machine,The effects of magnetic field intensity and graded pressure difference on dendrite morphology,orientation,secondary dendrite spacing(SDAS)and density of ZL114A samples with different axial diameters were systematically analyzed.The solidification behavior of the alloy under alternating magnetic field-pressure cooperative field was revealed,and the convection-extrusion infiltration equation of melt under alternating magnetic field-pressure cooperative field was established.The results indicate that under the cooperative field,melt particles continue to move under the influence of Lorentz force and pressure,accompanied with primary dendrite fragmentation,plankton,secondary growth and deformation,so that the solidification structure tends to be equiaxialized and the coarse dendrite turns into fine rose-crystal.In addition,the XRD pattern shows that the diffraction peak intensity of main crystal plane(111)is increased with the increase of magnetic field intensity,which confirms that alternating magnetic field can promote the preferential growth of dendrites on low-order crystal plane.Under the strong magnetic field,the metal atoms move violently,which causes the melt to overheat and affect solidification,leading to microstructure coarsening.Therefore,with the increase of magnetic field strength,the SDAS of alloy is decreased firstly and then increased,and the induced density is increased firstly and then decreased.The optimal treatment strength is 24 mT,where the increase of the fractional pressure difference is beneficial to dendrite refinement and solidification feeding.

关 键 词：真空差压铸造 铝合金 交变磁场 压力场 

分 类 号：TG249.2[金属学及工艺—铸造] TG146.21[一般工业技术—材料科学与工程]