中文摘要：

通过比较4种实验条件下Cu-80％Pb（质量分数）过偏晶合金的凝固组织，研究了冷速、磁场对过偏晶合金组织中富Cu相的形态和形成机制的影响．实验结果表明，球形富Cu相主要有3种形态，即“网壳型”、“卵型”、“眼型”．冷速对Cu-80％Pb宏观和微观组织有较大的影响．随着冷速的降低，Pb基体中的富Cu相由细小的球形转变为上浮聚集的粗大球形，直至全部上浮至试样顶部，富Pb基体中只保留Cu枝晶．冷速的降低使得富Cu球壳的厚度增加，其内部的网状组织粗化；施加12T强磁场能够抑制富Cu液滴的上浮和富Pb相的沉积，对Cu—Pb合金的重力偏析产生一定的抑制作用，所得到的偏晶合金宏观和微观组织与无磁场时冷速较快的组织类似．对于较大的富Cu液滴，强磁场具有抑制Cu溶质迁移的作用，抑制了球壳的增厚和网状组织的粗化．对有无磁场作用下富Cu液滴受到的作用力和运动终端速度进行了分析和计算．

英文摘要：

The solidification processes of Cu-80%Pb （mass fraction） hypermonotectic alloy were investigated at four experimental conditions. The formation process and morphology of Cu rich phase have been analyzed, and the influences of high magnetic field and cooling rate have been considered. The results show that the morphology of spherical Cu rich phases mainly has three kinds of microstructure, that is the larger ＂ net-shell type ＂, the smaller ＂ egg-type ＂ and＂ eye-type ＂. The cooling rate of the samples has great effect on both macrostructure and microstructure. As the cooling rate became slow, the Cu rich phase changed from the fine sphere to the larger floating sphere and the final coarse dendrite, the thickness of Cu-shell increased and net-like structure in Cu rich sphere phase coarsened; The 12 T high magnetic field has the effect on inhibiting the gravity segregation of Cu-Pb alloy by preventing the floation of larger Cu rich droplets and deposition of Pb matrix, the macrostructure and microstructure of Cu-Pb monotectic alloy similar to those under a relative fast cooling rate formed. And the 12 T high magnetic field maybe has the effect to inhibit the transition of Cu solute both outside and inside of Cu rich sphere phase, the Cu rich shell and the Cu-Pb ＂ net-like ＂ phase are not coarsened. The magnetic drag force and final velocity of droplets is analyzed and calculated, to show the influence of magnetic field.