Effect of alloying elements on the gamma to alpha transformation in steel. I
Effect of alloying elements on the gamma to alpha transformation in steel. I
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DOI：
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发表时间：
2002
期刊：
影响因子：
9.4
通讯作者：
J. Odqvist;M. Hillert;J. Ågren
中科院分区：
文献类型：
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作者：
J. Odqvist;M. Hillert;J. Ågren
用一个新编制的计算机程序模拟了Fe-Ni-C合金中α-γ的无分配生长，并考虑了所谓的溶质阻力，计算了界面内扩散和镍峰向前推进所引起的吉布斯能的耗散，可以显示出α/γ界面处的条件是如何随速度变化的。从准平衡状态到准平衡状态的连续变化可以在相图中说明。通过与近似的分析生长方程相结合，可以导出作为时间函数的α的厚度。生长速度被假定为在非常高的值开始，但由于碳的堆积而降低。对于合金组合物以外的准paraconditions和内部的限制增长被预测突然停止时，在反应过程中接近临界条件。对于合金成分进一步内的限制，没有这样的停止，除了由碳扩散场的冲击作用。在次平衡和准次条件的线之间的某个地方，a的最终厚度有一个相当快的下降。为了解释关于这种下降的实验信息，必须接受镍向α/γ界面偏析的明显趋势。
A newly constructed computer program was used to simulate partitionless growth of alpha in gamma of Fe-Ni-C alloys, taking into account so-called solute drag by evaluating the dissipation of Gibbs energy due to diffusion inside the interface and in the nickel spike being pushed in front of it. It could be shown how the conditions at the alpha/gamma interface vary with the velocity. A continuous change from paraequilibrium to quasi-paraconditions could be illustrated in the phase diagram. By combination with an approximate analytical growth equation, it was possible to derive the thickness of a as function of time. The growth velocity was assumed to start at very high values but decreased due to the pile-up of carbon. For alloy compositions outside the limit for quasi-paraconditions and just inside it the growth was predicted to stop suddenly when critical conditions are approached during the reaction. For alloy compositions further inside the limit, there was no such stop, except by the action of impingement of diffusion fields for carbon. Somewhere between the lines for paraequilibrium and quasi-paraconditions there is a rather rapid drop of the final thickness of a. In order to explain experimental information on this drop one must accept an appreciable tendency of segregation of nickel to the alpha/gamma interface.