外部冷却条件对激光熔凝Ni-Sn合金反常共晶形成的影响  

External Cooling Condition Effects on Formation of Anomalous Eutectic in Ni-Sn Alloy by Laser Remelting

作　　者：汪志太[1,2] 林鑫[1] 曹永青[1] 黄卫东[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072 [2]南昌航空大学工程训练中心,江西南昌330063

出　　处：《中国激光》2014年第12期91-96,共6页Chinese Journal of Lasers

基　　金：国家973计划(2011CB610402);国家863计划(2013AA031103);国家自然科学基金(51323008);高等学校博士学科点专项科研基金(20116102110016)

摘　　要：分别对置于铜、钛及耐火砖导热台上的Ni-33%Sn(质量分数,下同)合金进行激光熔凝实验,以研究不同的导热条件下激光重熔对Ni-33%Sn合金微观组织的影响。结果显示,在Ni-33%Sn合金试样被熔透的条件下,三种不同导热台上试样微观组织比较相似,熔池底部均产生了反常共晶组织,并且铜台上试样反常共晶区域明显大于其他两种导热台。分析认为,试样熔池底部的自由形核及快速生长导致了反常共晶的产生,而熔池两侧的外延生长行为以及熔池底部在经历高速自由形核生长后的外延生长条件的建立,使得只能在熔池底部的小区域内形成反常共晶。铜导热台由于具有更大的导热系数使得铜台上试样在底部有更大的冷却速率,从而获得更大的形核区域,所以该导热台上试样底部反常共晶区域要大于其他两种导热台的共晶区域。Microstructure evolution of Ni-33%Sn （mass fractiion, similarly hereinafter） alloys during laser remelting is investigated by placing on the copper plate, titanium plate and refractory brick, respectively. The result shows that the microstructure of samples on three different cooling plates is quite similar as for thoroughly melting of Ni-33 % Sn alloy and the anomalous eutectic structure can be obtained at the bottom of the molten pool. The area of anomalous eutectic on copper plate is significantly larger than those on the other two cooling plates. Free nucleation at the bottom of the molten pool and rapid growth lead to the generation of anomalous eutectic. The epitaxial growth behavior on both sides of the molten pool and the epitaxial growth conditions after high speed free nucleation and growth at the bottom of the molten pool lead to the small area of the anomalous eutectic at the bottom of the pool. The greater thermal conductivity of copper plate makes faster cooling rate and larger nucleation region at the bottom of the sample, which leads to larger area of anomalous eutectic than those of the other two cooling plates.

关 键 词：材料 激光熔凝 反常共晶 冷却条件 

分 类 号：TN249[电子电信—物理电子学] TG146[一般工业技术—材料科学与工程]