Effects of strain rate on mechanical properties and deformation behavior of an austenitic Fe-25Mn-3Al-3Si TWIP-TRIP steel
Effects of strain rate on mechanical properties and deformation behavior of an austenitic Fe-25Mn-3Al-3Si TWIP-TRIP steel
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DOI：
10.1016/j.msea.2017.11.017
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发表时间：
2018-01-10
期刊：
影响因子：
6.4
通讯作者：
Wittig, J. E.
中科院分区：
文献类型：
--
作者：
Benzing, J. T.;Poling, W. A.;Wittig, J. E.
研究了Fe-25 Mn-3Al-3Si（wt%）孪晶相变诱发塑性[TWIP-TRIP]钢在准静态和低动态应变速率（应变速率从点上= 10（-4）/s到点上= 10（2）/s）下的拉伸性能和变形机制。完全奥氏体显微组织主要通过位错滑移变形，但由于该合金的室温堆垛层错能[SFE]为21 +/- 3 mJ/m（2），二次变形机制如机械孪晶（TMF）和马氏体相变（TRIP）也在变形行为中起重要作用。机械孪晶和ε-马氏体片晶作为随后的位错运动在非共面滑移面上的平面障碍物，并减少位错的平均自由程。使用高速热摄像机测量试样温度的增加作为应变的函数，这使得使用热力学模型来预测SFE的增加。采用暗场透射电子显微镜、电子沟道衬度成像和电子背散射衍射对应变速率和应变对微观结构参数（如机械孪晶和ε-马氏体板条的厚度和间距）的影响进行了定量。还研究了板材厚度对力学性能的影响。拉伸试样厚度的增加使极限抗拉强度与总延伸率的乘积增大，但对均匀延伸率和屈服强度没有显著影响。的屈服强度表现出显着的增加，随着应变速率的增加，表明位错滑移变得更加困难，由于热激活的短程障碍。在较高的应变速率下，极限抗拉强度适度增加，均匀延伸率略有下降，表明绝热加热，应变硬化速率略有变化，观察到的应变局部化是根本原因，而不是在低应变值下基本TWIP-TRIP机制的显着变化。
The effects of quasi-static and low-dynamic strain rate ((epsilon) over dot = 10(-4)/s to (epsilon) over dot = 10(2)/s) on tensile properties and deformation mechanisms were studied in a Fe-25Mn-3Al-3Si (wt%) twinning and transformation-induced plasticity [TWIP-TRIP] steel. The fully austenitic microstructure deforms primarily by dislocation glide but due to the room temperature stacking fault energy [SFE] of 21 +/- 3 mJ/m(2) for this alloy, secondary deformation mechanisms such as mechanical twinning (TWIP) and epsilon martensite formation (TRIP) also play an important role in the deformation behavior. The mechanical twins and epsilon-martensite platelets act as planar obstacles to subsequent dislocation motion on non-coplanar glide planes and reduce the dislocation mean free path. A high-speed thermal camera was used to measure the increase in specimen temperature as a function of strain, which enabled the use of a thermodynamic model to predict the increase in SFE. The influence of strain rate and strain on microstructural parameters such as the thickness and spacing of mechanical twins and epsilon-martensite laths was quantified using dark field transmission electron microscopy, electron channeling contrast imaging, and electron backscattered diffraction. The effect of sheet thickness on mechanical properties was also investigated. Increasing the tensile specimen thickness increased the product of ultimate tensile strength and total elongation, but had no significant effect on uniform elongation or yield strength. The yield strength exhibited a significant increase with increasing strain rate, indicating that dislocation glide becomes more difficult with increasing strain rate due to thermally-activated short-range barriers. A modest increase in ultimate tensile strength and minimal decrease in uniform elongation were noted at higher strain rates, suggesting adiabatic heating, slight changes in strain-hardening rate and observed strain localizations as root causes, rather than a significant change in the underlying TWIP-TRIP mechanisms at low values of strain.