Composition-dependent phase substitution in directionally solidified Sn-22at.%Ni peritectic alloy
Composition-dependent phase substitution in directionally solidified Sn-22at.%Ni peritectic alloy
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DOI：
10.1007/s10853-015-9472-4
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发表时间：
2016-02
影响因子：
4.5
通讯作者：
P. Peng;Jieren Yang;Xinzhong Li;Yan-Qing Su;Jingjie Guo;H. Fu
中科院分区：
文献类型：
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作者：
P. Peng;Jieren Yang;Xinzhong Li;Yan-Qing Su;Jingjie Guo;H. Fu
首次在定向凝固 Sn-22at.%Ni 包晶合金中观察到凝固过程中初生 Ni3Sn2 相被包晶 Ni3Sn4 相生长替代。这种相替代现象对生长距离的依赖性以及因此对液相组成的依赖性已得到证实，这与目前认为生长应与距离无关的理解存在显着偏差。这种取代过程是由于初生 Ni3Sn2/包晶 Ni3Sn4 相生长过程中固/液界面处熔体浓度的连续变化引起的，这些初生 Ni3Sn2/包晶 Ni3Sn4 相是具有窄溶解度范围的金属间化合物。提出了基于凝固过程中溶质守恒的分析模型来描述这一相替代过程，该模型与实验结果非常吻合。此外，相替换所需的生长距离与生长速度成反比。研究还表明，在含有窄溶解度范围的金属间化合物的包晶体系（例如 Sn-Ni 包晶合金）的生长过程中，无法实现稳态熔体浓度。这表明此类合金在凝固过程中无法获得稳态生长。
Growth substitution of the primary Ni3Sn2phase by peritectic Ni3Sn4phase during solidification has been observed for the first time in directionally solidified Sn-22at.%Ni peritectic alloy. Dependence of this phase substitution phenomenon on growth distance, and thus composition of liquid phase has been confirmed, which shows significant deviations from the present understanding that the growth should be distance-independent. This substitution process is shown to arise from the continuous variation in melt concentration at the solid/liquid interface during growth of primary Ni3Sn2/peritectic Ni3Sn4phases which are intermetallic compounds with narrow solubility ranges. An analytical model based on solute conservation during solidification has been presented to describe this phase substitution process, which gives well agreement with the experimental results. Besides, the growth distance required for phase substitution is inversely proportional to the growth velocity. It has also been demonstrated that the steady-state melt concentration could not be achieved during growth of peritectic systems containing intermetallic compounds with narrow solubility range, such as Sn-Ni peritectic alloys. This indicated that steady-state growth can not be obtained during solidification this kind of alloys.