Flow stress analysis for determining the critical condition of dynamic ferrite transformation in 6Ni–0.1C steel
Flow stress analysis for determining the critical condition of dynamic ferrite transformation in 6Ni–0.1C steel
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DOI：
10.1016/j.actamat.2012.09.043
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发表时间：
2013
期刊：
影响因子：
9.4
通讯作者：
N. Park;A. Shibata;D. Terada;N. Tsuji
中科院分区：
文献类型：
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作者：
N. Park;A. Shibata;D. Terada;N. Tsuji
为了阐明 6Ni-0.1C 钢中动态铁素体相变的发生情况，分析了大范围温度和应变速率下单轴压缩的应力应变行为。在较低温度和恒定应变速率下观察到奥氏体流变应力的显着软化，这似乎与铁素体动态转变的发生相对应。对应力-应变曲线中最大应力的分析表明，动态铁素体相变发生在齐纳-霍洛蒙参数 (Z) 一定值以上。确定了发生动态转变的临界变形条件（ZC）。软化量的增加导致铁素体含量的增加，最大流变应力接近于铁素体的流变应力。微观结构观察表明，表现出软化的试样由具有典型变形微观结构特征的铁素体晶粒组成，例如铁素体晶粒内晶体取向的变化、铁素体形态的不均匀性和晶粒内部的位错亚结构。所有这些特征都证实了变形过程中铁素体相变的发生，即动态铁素体相变。
In order to clarify the occurrence of dynamic ferrite transformation in a 6Ni–0.1C steel, the stress–strain behavior in uniaxial compression was analyzed for a wide range of temperatures and strain rates. Significant softening of flow stress for austenite was observed at lower temperatures at a constant strain rate, which seemed to correspond with the occurrence of dynamic transformation to ferrite. Analysis of the maximum stress in the stress–strain curves indicated that dynamic ferrite transformation occurred above a certain value of the Zener–Hollomon parameter (Z). The critical deformation condition (ZC) for the occurrence of dynamic transformation was determined. Increasing the amount of softening resulted in an increase in the fraction of ferrite, and the maximum flow stress came close to the flow stress of ferrite. Microstructural observations revealed that the specimens exhibiting softening consisted of ferrite grains with typical characteristics of deformation microstructure, such as a change in crystal orientation within the ferrite grain, inhomogeneity in ferrite morphology and dislocation substructures inside the grains. All these characteristics confirmed the occurrence of ferrite transformation during deformation, i.e. dynamic ferrite transformation.