强磁场对定向凝固Al-4.5Cu合金微观偏析的影响  

EFFECT OF A HIGH STATIC MAGNETIC FIELD ON MICROSEGREGATION OF DIRECTIONALLY SOLIDIFIED Al-4.5Cu ALLOY

作　　者：钟华[1] 李传军[1] 王江[1] 任忠鸣[1] 钟云波[1] 玄伟东[1] 

机构地区：[1]上海大学省部共建高品质特殊钢冶金与制备国家重点实验室,上海200072

出　　处：《金属学报》2016年第5期575-582,共8页Acta Metallurgica Sinica

基　　金：国家重点基础研究发展计划项目2011CB010404;国家自然科学基金项目51404148和51401116;上海市科学技术委员会项目13DZ1108200;13521101102和14521102900资助~~

摘　　要：研究了强静磁场对定向凝固Al-4.5Cu(质量分数,%)合金微观偏析的影响.结果表明,强磁场显著影响了凝固组织中非平衡第二相的形态和数量.无磁场时,粗大的第二相为网络状,连续分布于晶界上;施加磁场后,晶界上连续分布的第二相被打断,其面积分数随磁场强度的增加而减小.在磁场作用下,溶质原子的再分配行为发生改变,Cu溶质成分曲线降低,有效分配系数ke减小.上述现象主要是由于磁场在熔体中引发热电磁对流以及由热电磁对流驱动的二次流,在糊状区内产生搅拌,改变溶质传输行为.Microsegregation is the unbalanced distribution of alloying element between solid and liquid phases in dendritic scale during solidification. The solute redistribution usually leads to the formation of brittle secondary phase, which is harmful to the workability and final mechanical properties of casting component. It has been accepted that fluid flow plays a critical role in mass transfer during solidification and thus altering the microsegregation pattern. High static magnetic field has been considered as an effective way to control the convection in solidification. In this work, the impact of the high static magnetic field on the microsegregation was investigated. Al-4.5Cu（mass fraction, %） alloy was directionally solidified from 001 seed crystal under various magnetic fields with a constant pulling rate of 50 μm/s and temperature gradient of 101 K/cm. OM and BSE were applied to characterize the microstructure of the solidified samples. The fraction of Al2 Cu second phase was obtained by software analysis from the transverse and longitudinal sections. The results show that the Al-4.5Cu alloy solidifies in dendritic morphology. The formation of second phase is significantly affected by the magnetic field. Without magnetic field, the continuous network of second phase is observed at grain boundaries. In the presence of the magnetic field, the second phase is disconnected in the grain boundaries and dispersed in grains. The fraction of the second phase is reduced with the increase of the magnetic field. EDS area scan was carried out to measure the concentration of Cu solute in dendritic scale. Isoconcentration contour maps of Cu in the plane perpendicular to the primary dendrite trunk were drawn. The concentration profiles of Cu were plotted from the measured data and the effective partition coefficient kewas calculated. It is found that the redistribution of Cu solute in interdendritic region is greatly altered by the magnetic field. When the intensity of the magnetic field increases, the concentration prof

关 键 词：AL-4.5CU合金 强磁场 定向凝固 微观偏析 有效分配系数 热电磁对流 

分 类 号：TG146[一般工业技术—材料科学与工程]