Modeling the creep threshold stress due to climb of a dislocation in the stress field of a misfitting precipitate
Modeling the creep threshold stress due to climb of a dislocation in the stress field of a misfitting precipitate
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DOI：
10.1016/j.actamat.2011.04.044
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发表时间：
2011-08
期刊：
影响因子：
9.4
通讯作者：
M. Krug;D. Dunand
中科院分区：
文献类型：
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作者：
M. Krug;D. Dunand
建立了由共格、失配析出物强化的合金蠕变门槛应力模型，该模型适用于析出物未被剪切且位错与其爬过的析出物之间存在弹性相互作用的情况。由于析出物和基体之间的正刚度和晶格参数失配引起的颗粒应力场的计算预测，失配力有助于位错在析出物上的爬升/滑动过程，但它们将位错捕获在颗粒的离开侧。这导致了真正的门槛应力，而不是像在以前的模型中那样，位错攀升动力学的减慢，这是由通过滑动机制释放位错所需的外加应力提供的。对含有不同尺寸和不同失配的纳米Al3Sc、Al3(Sc，Li)和Al3(Sc，Yb)相的析出强化铝合金进行了模型预测和实验比较。与蠕变实验结果一致的是，该模型预测门槛应力与析出相半径以及析出相/基质晶格失配的大小几乎成线性关系。
A model for creep threshold stresses in alloys strengthened by coherent, misfitting precipitates is developed for the case where the precipitate is not sheared, and where there are elastic interactions between a dislocation and the precipitate over which it climbs. Calculations of the particle stress field due to a positive stiffness and lattice parameter mismatch between precipitate and matrix predict that the mismatch forces help the dislocation climb/glide process over the precipitates but that they trap it at the departure side of the particle. This results in a true threshold stress, rather than a slowing of the kinetics of dislocation climb as in previous models, which is given by the applied stress necessary to free the dislocation by a glide mechanism. Model predictions and experiment are compared for precipitation-strengthened aluminum alloys containing nanosize Al3Sc, Al3(Sc, Li) and Al3(Sc, Yb) precipitates with various sizes and mismatches. In agreement with experimental creep results, the model predicts that the threshold stress increases nearly linearly with precipitate radius, and also with the magnitude of the precipitate/matrix lattice mismatch.