多级雾化锡-铅合金的大过冷和凝固

STUDIES ON LARGE UNDERCOOLING ANDSOLIDIFICATION OF MULTISTAGE ATOMIZED TIN LEAD ALLOY

ｎＰｂ合金经多级雾化后，得到平均粒度１０～２０μｍ的快速凝固粉末。采用差热分析（ＤＴＡ）和扫描电镜分析（ＳＥＭ）对ＳｎＰｂ多级雾化粉末的过冷度和结构进行了研究，结果表明：多级雾化的确存在熔体的大过冷，与理论预言相吻合，测得的过冷度（在低冷速下）最高时超过９０Ｋ。过冷度与熔滴成分密切相关，富Ｓｎ合金过冷度大于富Ｐｂ合金。粉末的显微组织结构强烈依赖于过冷度、形核前的冷却速度和合金成分。过冷度越大，冷速越大，组织越细小均匀。

After multistage atomization of Sn Pb alloy, rapidly solidified powders with a median diameter of 10 to 20 μm were obtained. DTA and SEM analysis were adopted to study the undercooling and structure of multistage atomized tin lead droplets emulsified in an organic oil, polyphenylether. The results showed that there is large undercooling of melt indeed in multistage atomization, which agrees with the theoretical prediction. The maximum undercooling measured (under low cooling rate) is up to more than ninety degrees. Undercoolings achieved in tin lead alloy atomized droplets depend to a considerable extent on the composition of the melts, tin rich alloys undercool more than lead rich alloys. The microstructure of the droplets depend heavily on undercooling, cooling rate before nucleation and alloy composition, the larger the undercooling and the cooling rate are, the finer the microstructure of the droplets is.