对Co-93.0%Sb(质量分数)合金进行了Bridgman定向凝固和激光快速凝固实验,利用XRD, SEM和EDS分析了合金凝固组织中的相组成和成分分布.结果表明, 在Bridgman定向凝固速率为2和5μm/s时, 合金凝固组织只有CoSb₃和Sb 2相;而当凝固速率为20, 50, 100和500 μm/s时, 组织由初生相CoSb₂, 包晶相CoSb₃和Sb相组成,凝固组织中CoSb₃体积分数随凝固速率的增加而减少. 激光快速凝固方法中, 当扫描速率为5 mm/s时,组织有CoSb₂, CoSb₃和Sb 3相; 而当扫描速率增大到10, 20和50 mm/s时,包晶相CoSb₃取代初生相CoSb₂直接析出, 合金凝固组织只有CoSb₃和Sb 2相,根据凝固理论计算得出, 包晶相直接析出的临界速率为7.61 mm/s, 与实验结果相吻合.另外, 低定向凝固速率2-5 μm/s下获得CoSb₃是因为有足够的凝固时间促进包晶反应进行,而激光快速凝固下, 凝固速率大于10 mm/s时, CoSb₃是通过液相直接凝固获得的.要获得大体积分数的CoSb₃相, 需采用较低的定向凝固速率.

The compound CoSb₃ is one kind of thermoelectric material that has been received more attention due to its potential application in green refrigeration and power generation. The general way to prepare CoSb₃ material is sintering and the solidification behavior of CoSb₃ compound is rarely reported, since this compound is obtained through the peritectic reaction, and there exists phase competitive growth in solidification process. In this work, Bridgman directional solidification and laser rapid solidification experiments on Co-93.0%Sb (mass fraction) alloy were carried out. XRD, SEM and EDS were employed to determine the solidified phases and characterize the microstructure. The results showed that for Bridgman directional solidification, the solidification microstructure of Co-93.0%Sb alloy contained only the CoSb₃ and Sb phases at the solidification rates of 2 and 5 μm/s, whereas at the solidification rates of 20, 50, 100 and 500 μm/s, the microstructure contained CoSb₃, CoSb₂ and Sb phases. Furthermore, the volume fraction of CoSb₃ phase decreased with increasing solidification rate. For laser rapid solidification, the solidification microstructure consisted of CoSb₃, CoSb₂ and Sb phases at the scanning rate of 5 mm/s. As the scanning rate ranging from 10 to 50 mm/s, the microstructure is composed of only CoSb₃ and Sb phases. The critical rate of peritectic phaseCoSb₃ instead of primary CoSb₂ solidified directly from the melt was theoretically predicted to 7.61 mm/s, agreeing well with the experiment result. In addition, the formation mechanisms of peritectic phase CoSb₃ at Bridgeman directional solidification and laser rapid solidification were analysed. The formation of peritectic phase at low solidification rates was due to the local solidification time available for the peritectic reaction, and at high solidification rates higher than 10 mm/s the peritectic phase CoSb₃ was obtained directly from the melt. Therefore to obtain a large volume fraction of peritectic phase CoSb₃,  a low solidification rate is recommended.