SnSb15合金液-液结构转变的可逆性及熔体状态对凝固的影响

摘要

In order to study the reversibility of liquid­liquid structure transition (L­LST) and the effects of melt state on solidification, the electrical resistivity­temperature curves of SnSb15 melt were measured in three heating and cooling cycles by means of DC four­probe method. The physical connotation of irreversible and reversible L­LST was analyzed, and the effects of irreversible L­LST on solidification were also discussed. The results show temperature induced L­LST occurs in SnSb15 melt. L­LST in first heating process is irreversible, but it is reversible in subsequent cooling and heating processes. Besides, irreversible L­LST can significantly affect the solidification behavior and microstructure, i.e. the undercooling degrees for primary and peritectic phase enlarge 9.7 and 5℃, the solidification time shortens 2.5 and 4 s, respectively. Moreover, the solidification microstructures are refined obviously.%　　为了探讨液−液结构转变的可逆性及熔体状态对凝固的影响，利用直流四电极法测量SnSb15合金熔体在三轮连续升降温过程中的电阻率−温度曲线。分析SnSb15合金熔体的不可逆和可逆转变的物理内涵，进而讨论不可逆转变对凝固影响的作用机制。结果表明：SnSb15合金熔体发生了温度诱导的液−液结构转变，其首轮升温过程的转变呈不可逆性，而后续降温及升温过程的转变呈可逆特征；且首轮升温过程的不可逆液−液结构转变显著影响合金的凝固行为和组织，如初生相和包晶相的形核过冷度分别增大9.7和5℃，凝固时间分别缩短2.5和4 s，并且凝固组织明显细化。