Abstract A model is proposed explaining enhanced strength of ultrafine-grained alloys that contain grain boundary (GB) solute segregations. In the framework of the proposed model these segregations are treated as homogeneous ellipsoidal inclusions and act as the sources of elastic stresses affecting the emission of lattice dislocations from GBs. These segregations pin the ends of lattice dislocation segments at the initial stage of dislocation propagation along GBs, and the unpinning requires a load increase, leading to the enhanced yield strength. We calculate the contribution of GB segregations to the yield strength for the ultrafine-grained 1570 Al alloy. We demonstrate that the maximum yield strength of this alloy is achieved in the case of clustered, nearly spherical Mg segregations with a high Mg concentration and a diameter to thickness ratio of 1.0–1.4, depending on the Mg concentration inside segregations. We also briefly discuss the possible role of non-equilibrium GB dislocations in the formation of such concentrated solute segregations as well as the influence of GB segregations on the strengthening of alloys containing nanoscale twins. The results of the calculations agree well with experimental data.

中文翻译：

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超细晶合金中晶界溶质偏析引起的强度增强

摘要 提出了一个模型来解释包含晶界 (GB) 溶质偏析的超细晶粒合金的强度增强。在所提出的模型的框架中，这些偏析被视为均质的椭球夹杂物，并作为影响 GB 晶格位错发射的弹性应力来源。在位错沿 GB 传播的初始阶段，这些偏析将晶格位错段的末端钉住，而解除钉扎需要增加载荷，从而提高屈服强度。我们计算了 GB 偏析对超细晶 1570 铝合金屈服强度的贡献。我们证明了这种合金的最大屈服强度是在聚集的情况下实现的，近球形的 Mg 偏析，具有高 Mg 浓度和 1.0-1.4 的直径与厚度比，这取决于偏析内部的 Mg 浓度。我们还简要讨论了非平衡 GB 位错在形成这种集中溶质偏析中的可能作用，以及 GB 偏析对含有纳米级孪晶的合金强化的影响。计算结果与实验数据吻合良好。