Microstructural evolution during grain boundary engineering of low to medium stacking fault energy fcc materials
Microstructural evolution during grain boundary engineering of low to medium stacking fault energy fcc materials
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DOI：
10.1016/s1359-6454(02)00090-3
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发表时间：
2002-06
期刊：
影响因子：
9.4
通讯作者：
Mukul Kumar;A. Schwartz;W. King
中科院分区：
文献类型：
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作者：
Mukul Kumar;A. Schwartz;W. King
晶界工程包括这样的过程，通过该过程，操纵微观结构中所谓的特殊和随机晶界的相对分数，目的是改善材料性能，例如耐腐蚀性、抗蠕变性和可焊性。一种这样的工艺也被称为顺序热机械处理（TMP），其包括适度应变，然后在相对高的温度下短时间退火。这些热机械处理fcc金属和合金具有低到中等堆垛层错能的结果在微观结构中具有高分数的303和其他特殊边界，如重合位置晶格（CSL）模型所定义的。更重要的是，随机边界的互连网络作为处理的结果被显著修改。在晶界网络的修改已与死后的电子背散射衍射（EBSD）和透射电子显微镜（TEM）观察的变形和退火状态的材料。的微观结构的演变到一个高分数的x3n边界与不动的边界在退火过程中的分解或解离。这是由TEM观察到的相对不移动的边界分解成两个组件，一个具有非常低的能量，因此不移动的，和另一个高度移动的边界迁移到邻近地区的更高的应变水平证明。低能量晶界的形成，通过这种机制及其对边界网络拓扑结构的影响进行了讨论的背景下，晶界工程和已知的微观结构的演变机制。
Grain boundary engineering comprises processes by which the relative fractions of so-called special and random grain boundaries in microstructures are manipulated with the objective of improving materials properties such as corrosion, creep resistance, and weldability. One such process also referred to as sequential thermomechanical processing (TMP), consists of moderate strains followed by annealing at relatively high temperatures for short periods of time. These thermomechanical treatments on fcc metals and alloys with low to medium stacking fault energies result in microstructures with high fractions of Σ3nand other special boundaries, as defined by the coincidence site lattice (CSL) model. More importantly, the interconnected networks of random boundaries are significantly modified as a consequence of the processing. The modifications in the grain boundary network have been correlated with post-mortem electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations of the deformed and annealed states of the material. The evolution of the microstructure to a high fraction of Σ3nboundaries is correlated with the decomposition or dissociation of immobile boundaries during annealing. This is evidenced by TEM observations of the decomposition of relatively immobile boundaries into two components, one with very low energy and thus immobile, and the other a highly mobile boundary that migrates into neighboring areas of higher strain levels. The formation of low-energy grain boundaries through this mechanism and its effect on boundary network topology is discussed within the context of grain boundary engineering and linked to known microstructural evolution mechanisms.