Modeling Bainite Transformation and Retained Austenite in Hot Rolled TRIP Steel by Instantaneous Carbon Enrichment
Modeling Bainite Transformation and Retained Austenite in Hot Rolled TRIP Steel by Instantaneous Carbon Enrichment
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DOI：
10.1002/srin.201700122
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发表时间：
2017-09
影响因子：
2.2
通讯作者：
P. Suwanpinij;Xiaoxiao Li;U. Prahl;W. Bleck
中科院分区：
文献类型：
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作者：
P. Suwanpinij;Xiaoxiao Li;U. Prahl;W. Bleck
继承Leblond和Devaux概念的速率模型已被应用于热轧TRIP钢的多相转变。相分数来自不同实验室规模的过程模拟，包括重复再结晶的多道次轧制和单道次循环。用原位同步辐射X射线衍射仪对后者进行了研究，获得了相组成和碳含量的瞬时数据。不同的循环允许不同的奥氏体调制度输入，以扩大热机械参数的范围。贝氏体相变模型是残余奥氏体内瞬时平均碳含量的函数，它是由一维衍射峰的移动测量得到的。该模型可以为TRIP钢的特定所需组织映射不同的工艺窗口。低碳含量显著有利于贝氏体的形成。但是，前一步中铁素体的形成促进了碳含量的增加，贝氏体量减少，从而允许较大比例的残余奥氏体量。根据原位X射线衍射仪的数据建立了修正的Koistinen-Marburger方程来模拟马氏体在终冷过程中的形成，从而揭示了奥氏体相的稳定性。超过1.475%的平均碳含量，残余奥氏体会变得稳定。
The rate model inherited from Leblond and Devaux's concept has been applied to multiphase transformations in hot‐rolled TRIP steel. The phase fraction is collected from different laboratory scale process simulations, both multi‐pass rolling for repeated recrystallization and single‐pass cycles. The latter is also investigated by in situ synchrotron X‐ray diffraction (XRD) to acquire instantaneous data for the phase fraction and carbon content. The different cycles allow different austenite conditioning inputs for the model to enlarge the range of thermomechanical parameters. Bainite transformation model is a function of the instantaneous average carbon content in the remaining austenite, which is measured from the shift in the 1‐dimensional diffraction peaks. The modeling can map different process windows for a specific required microstructure of TRIP steel. The bainite formation is remarkably favored by low carbon content. But, the promotion of ferrite formation in the former step increases the carbon content dramatically and yields smaller bainite fraction that consequently larger fraction of retained austenite is allowed. A modified Koistinen–Marburger equation has been established from the in situ XRD data to model the martensite formation during the final cooling to reveal the stability of austenite. Above an average carbon content of 1.475 mass%, the retained austenite becomes stable.