The role of coincidence-site-lattice boundaries in creep of Ni-16Cr-9Fe at 360 °C
The role of coincidence-site-lattice boundaries in creep of Ni-16Cr-9Fe at 360 °C
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DOI：
10.1007/s11661-997-0167-6
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发表时间：
1997-10
期刊：
影响因子：
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通讯作者：
V. Thaveeprungsriporn;G. Was
中科院分区：
文献类型：
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作者：
V. Thaveeprungsriporn;G. Was
本研究的目的是了解和量化符合点晶格边界（CSLB）种群对Ni-16Cr-9Fe在360°C下蠕变变形的作用。假设CSLB种群的增加降低了晶界位错湮灭率，导致内应力增大，有效应力减小。其结果是蠕变应变率的降低。因此，cslb在变形中的作用是通过捕获晶界上的磨合晶格位错作为外在晶界位错（egbd）来增加内应力，在随后的位错上产生背应力，而不是像在高角晶界（HABs）的情况下消除它们。该假设得到了证实，表明(1)CSLB和HAB之间的位错吸收动力学存在很大差异，(2)CSLB组分强烈影响固体中的内应力。通过透射电镜（TEM）对比EGBD密度测定了位错吸收动力学。结果表明，在菌株1.25%时，CSLBs中EGBD的含量是HABs的3倍。通过应力倾角试验测量内应力，发现cslb增强试样的内应力提高了约30 MPa。Ni-16Cr-9Fe在360℃氩气中的稳态蠕变速率也受到晶界特征分布的强烈影响。将CSLB组分增加约2倍，在粗晶（330µm）样品中稳态蠕变率降低8至26倍，在小晶（35µm）样品中降低40至66倍。假设egbd的湮灭只发生在至少两个赤潮相交的三线处。通过使用几何关系来评估egbd在三线处湮灭的概率，该模型预测了蠕变速率与CSLB分数的非线性依赖关系，并与测量结果产生了良好的相关性。该模型为适量增加CSLB分数可以大大降低Ni-16Cr-9Fe中的稳态蠕变速率提供了物理基础。
The objective of this study is to understand and quantify the role of the coincidence-site-lattice boundary (CSLB) population on creep deformation of Ni-16Cr-9Fe at 360 °C. It is hypothesized that an increase in the CSLB population decreases the annihilation rate of dislocations in the grain boundary, leading to an increase in the internal stress and a decrease in the effective stress. The result is a reduction in the creep strain rate. The role of CSLBs in deformation is, thus, to increase the internal stress by trapping run-in lattice dislocations at the grain boundaries as extrinsic grain boundary dislocations (EGBDs), creating backstresses on following dislocations rather than annihilating them, as in the case of high-angle boundaries (HABs). The hypothesis was substantiated by showing (1) that dislocation absorption kinetics differ substantially between a CSLB and an HAB, and (2) that the CSLB fraction strongly affects the internal stress in the solid. Dislocation absorption kinetics were measured by comparing EGBD density in transmission electron microscopy (TEM). Results showed that CSLBs contain an EGBD density which is 3 times higher than HABs at 1.25 pct strain. Internal stress was measured by the stress dip test and was found to be ≈ 30 MPa higher in the CSLB-enhanced sample. Steady-state creep rates of Ni-16Cr-9Fe in 360 °C argon were also found to be strongly affected by the grain boundary character distribution. Increasing the CSLB fraction by approximately a factor of 2 resulted in a decrease in steady-state creep rates by a factor of 8 to 26 in coarse-grain (330µm) samples and a factor of 40 to 66 in small-grain (35µm) samples. It is postulated that annihilation of EGBDs only occurs at triple lines where at least two HABs intersect. By using a geometric relationship to evaluate the probability of EGBDs annihilating at a triple line, the model predicts a non-linear dependence of the creep rate with CSLB fraction, yielding excellent correlation with measurement. The model provides a physical basis for measurements which show that increasing the CSLB fraction by only moderate amounts can greatly reduce the steady-state creep rate in Ni-16Cr-9Fe.