Dynamics Study on Morphological Stabilities of Cellular Crystal Lateral Wall
Dynamics Study on Morphological Stabilities of Cellular Crystal Lateral Wall
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DOI：
10.1007/s11661-011-1008-1
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
G. Chang;Shu-ying Chen;Qing-chun Li;Xu-dong Yue;Guang-can Jin
中科院分区：
文献类型：
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作者：
G. Chang;Shu-ying Chen;Qing-chun Li;Xu-dong Yue;Guang-can Jin
本文研究了熔体中胞状晶体生长过程中的侧壁稳定性。首先推导了熔体中圆柱固液界面形态稳定性的动力学方程，然后定义了圆柱固液界面形态稳定性判据的表达式。分析了形状因子、实体半径等相关因素对形态稳定性的影响。此外，还确定了保持界面稳定性的临界形状因子和临界生长速率。在高温共焦扫描激光显微镜（HTCSLM）下观察了碳钢δ相胞状晶体的横向生长过程，验证了理论分析和计算结果。结果表明，形状因子有利于提高胞状晶体侧壁的稳定性。然而，在胞状晶体半径增大的过程中，胞状晶体半径存在一定值，导致形状因子迅速降低胞状晶体侧壁的稳定性。即使其他条件不变，胞状晶体的形状也可能导致胞状晶体侧壁失去稳定性。在本研究条件下，有两个关键的生长速率可以保持细胞晶体侧壁稳定生长。对于 Fe-0.15 pct C-0.8 pct Mn 合金，这两个临界生长速率分别为 10−4 和 10 cm/s 数量级。两者相差105倍以上，因此慢临界增长率符合实际临界增长率。胞状晶体的半径是侧壁稳定性的主要影响因素。胞状晶体的半径越大，侧壁的稳定性越差。这也是细胞晶体能够在一定时期内存活的原因之一。胞状晶体侧壁稳定性的理论分析结果与HTCSLM观察到的碳钢δ相胞状晶体的横向生长现象非常吻合。径向临界增长率的理论计算结果与实验结果吻合。
The lateral wall stabilities during the growing process of cellular crystal in the melt were studied in this article. The dynamics equation of cylindrical solid-liquid interface morphological stabilities in melt was first derived, and then the expression of criterion for cylindrical solid-liquid interface morphological stabilities was defined. The effect of the shape factor, solid radius, and other relevant factors on the morphological stabilities was analyzed. Also, the critical shape factor and critical growth rate for keeping the stabilities of the interface were determined. The phenomenon during the lateral growth process ofδ-phase cellular crystal in carbon steel was observed under a high-temperature confocal scanning laser microscope (HTCSLM), which was used to verify the theoretical analysis and calculated results. The results indicate that the shape factor is beneficial to improving the stabilities of the cellular crystal lateral wall. During the increase process of the cellular crystal radius, however, there is a certain value of the cellular crystal radius, which induces the shape factor to reduce stabilities of the cellular crystal lateral wall rapidly. Even if the other conditions are unchanged, the shape of the cellular crystal may also cause the cellular crystal lateral wall to lose its stabilities. There are two critical growth rates to keep the cellular crystal lateral wall growing stably under the conditions of this research. For the Fe-0.15 pct C-0.8 pct Mn alloy, these two critical growth rates are 10−4and 10 cm/s orders of magnitude, respectively. The difference between them is more than 105times, so the slow critical growth rate conforms to the actual critical growth rate. The radius of the cellular crystal is the main influencing factor of lateral wall stabilities. The bigger the radius of the cellular crystal is, the worse the stabilities of the lateral wall are. That is also one of the reasons that the fine cellular crystal can survive during a certain period. The results of the theoretical analysis about stabilities of the cellular crystal lateral wall agree well with the lateral growth phenomena ofδphase cellular crystal in carbon steel observed by a HTCSLM. The theoretically calculated results of the radial critical growth rates are coincident with the experimental results.