【摘要】 采用永磁体旋转装置实现了Pb-50wt%Sn亚共晶、Pb-61.9wt%Sn共晶合金旋转磁场条件下的凝固,并对其凝固规律进行了研究。发现与常规条件下相比,旋转磁场导致的合金熔体内部强迫对流加快了合金熔体的冷却速率,提高熔体初始形核温度,促发熔体提前形核并能使凝固时间缩短。Pb-61.9wt%Sn共晶合金的宏观偏析被有效抑制,在整个样品中得到了二元共晶组织,共晶层片粗化,局域地区出现了不规则共晶组织。对于Pb-50wt%Sn亚共晶,初生相(Pb)的生长方式由粗大枝晶转变为细小的球状颗粒,且晶粒显著细化。更多还原

【Abstract】 The experiment of Pb-50wt%Sn,Pb-61.9wt%Sn alloy solidify in rotating magnetic field and the regularity of the process was carried out, The microstructure and growth characteristics were investigated. According to the cooling curves, The roating magnetic field tend to accelerate the cooling rate and stimulate the nucleation of the melt compared to static condition .The stirring effect of magnetic tend to provide some extra energy fluctutation to overcome the therm odynamic barrier for nucleation. It is found that,for Pb-61.9wt%Sn eutectic alloy,magnetic field induced the forced convection of the melt which result in a microstructure of lamellas →coarser lamellas→ anomalous eutectic"and suppression of gravity-microsegregation and it was revealed that a “lamellar eutecticanomalous eutectic”.Meanwhile, for Pb-50wt%Sn eutectic alloy, a “dendrite manner spheric grain” microstructre change of the primary phase (Pb)occurs and conspicuous grain refinement effect takes place .These are explained by the forced convection inside the melt.更多还原