Grain refinement and the stability of dendrites growing into undercooled pure metals and alloys
Grain refinement and the stability of dendrites growing into undercooled pure metals and alloys
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DOI：
10.1063/1.365740
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发表时间：
1997-10
影响因子：
3.2
通讯作者：
A. Mullis;R. Cochrane
中科院分区：
文献类型：
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作者：
A. Mullis;R. Cochrane
我们提出了一个分析的稳定性的枝晶对一个小的扰动尖端速度。我们发现纯金属和合金中的枝晶生长在过冷度上限ΔT2*以上将变得不稳定。在高于临界浓度的合金中，低于较低的临界过冷度（ΔT1*），枝晶生长也可能变得不稳定。在Ni-Cu和Ag-O的研究中，这些不稳定区域的位置与自发晶粒细化的开始非常接近。得到了195 K和160 K时Ni和Ag的ΔT2*值，与170 K和133 ~ 153 K时的观测值吻合较好。
We present an analysis of the stability of a dendrite against a small perturbation to the tip velocity. We find that dendritic growth in pure metals and alloys will become unstable above some upper critical undercooling ΔT2*. In alloys above a critical concentration, dendritic growth may also become unstable below a lower critical undercooling, ΔT1*. In the example systems studied, Ni–Cu and Ag–O, the location of these unstable regions shows remarkably close agreement with the onset of spontaneous grain refinement. We obtain values of ΔT2* for Ni and Ag of 195 K and 160 K, respectively, in good agreement with the observed values of 170 K and 133–153 K.