Phase separation and structural evolution of undercooled Fe–Sn monotectic alloy
Phase separation and structural evolution of undercooled Fe–Sn monotectic alloy
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DOI：
10.1016/s0921-5093(02)00471-9
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发表时间：
2003-03
期刊：
影响因子：
6.4
通讯作者：
Nan Wang;B. Wei
中科院分区：
文献类型：
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作者：
Nan Wang;B. Wei
Fe-48.8wt.%采用落管法和玻璃熔凝法快速凝固一元锡合金，研究了其相分离特征和组织演变。计算了不同尺寸液滴在落管中的冷却速率范围为7.0× 102 ~ 2.8× 104 K·s-1，液滴直径从800 μm减小到100 μm。随着重力加速度的减小，Marangoni运动的影响比Stokes运动的影响更显著，但对第二液相的弥散影响很小。计算结果表明，由于所需的过冷度很大，失稳分解很难发生。当液滴尺寸变化时，形核和长大表现出不同的特征。虽然富Sn液相从过冷熔体中分离出来，但它并不能显著改变母液相的组成，并且抑制了末端组分固体的生长，这一点通过玻璃助熔剂技术的本体过冷实验测量和计算的枝晶生长速度得到证实。液滴在落管中凝固时，由于凝固时间很短，在单相转变过程中很难形成枝晶。
Fe–48.8wt.% Sn monotectic alloy was rapidly solidified both in a drop tube and with the glass fluxing method, and its phase separation characteristics and structural evolution are investigated. The regime of cooling rate of different size droplets in the drop tube is calculated from 7.0×102to 2.8×104K s−1with a decrease of droplet diameter from 800 to 100 μm. The effect of Marangoni migration is more significant than that of Stokes motion with the decrease of gravitational acceleration, but it has a weak influence on the dispersion of the second liquid phase. The immiscibility gap is calculated and it shows that spinodal decomposition is difficult to occur because the necessary undercooling is quite large. Nucleation and growth show different characteristics when droplet size varies. Although the Sn-rich liquid phase separates from the undercooled melt, it cannot change significantly the composition of parent liquid phase, and the growth of terminal composition solid is suppressed, which is confirmed by the measured and calculated dendritic growth velocity by bulk undercooling experiments with the glass fluxing technique. Well-branched dendrites of the solid phase are difficult to form during monotectic transformation when droplets solidify in the drop tube owing to the very short solidification period.