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首页> 外文期刊>Materials Science and Engineering. A, Structural Materials >Do we have an acceptable model of power-law creep?
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Do we have an acceptable model of power-law creep?

机译：我们有幂律蠕变的可接受模型吗？

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Three models of power-law creep are frequently presented. Those of Weertman assume distributed sources of dislocations which spread until they meet dislocations from other sources. They then annihilate by bulk diffusion. If the density of sources is independent of stress, a 9/2 power law follows, but the creep rate is grossly less than that observed. Moreover, the more plausible assumption of a source density proportional to the cube of the stress leads to the conventional power law of 3. The model of Spingarn and Nix assumes dislocation glide with pile-ups at the grain boundaries. These cause steps on the boundaries, which are removed by grain-boundary diffusion. A fifth power law follows. The agreement in absolute creep rate shown in the original paper arises from a misreading of the tabulated data, and the true predicted creep rate is again far too low. Vacancy diffusion along dislocation cores in the interior of the grains is not likely to dominate grain-boundary diffusion, because the cross section of the dislocation network exceeds that of the grain boundary material only at large grain sizes. While Mecking and Estrin have shown that the vacancy concentration produced mechanically even in dislocation cell walls is likely to exceed that in thermal equilibrium only below 1/2 T_m, it seems possible that the highly mobile interstitials produced mechanically may migrate along dislocations of secondary glide systems to allow vacancy and interstitial dipoles of the primary system to annihilate mutually, with a probable power law of 5. However, the observations of Andrade and of Hanson, which may apply to the regime of power-law breakdown rather than power-law creep, strongly indicate that deformation is localized at the grain boundaries. If this is the case, existing theories of power-law creep based on models of homogeneous deformation are irrelevant; alternatively, the regimes of power-law creep and power-law breakdown must be treated separately.
机译：经常介绍三种幂律蠕变模型。韦尔特曼（Weertman）的研究者假定位错的分布源不断扩散，直到遇到其他来源的位错。然后，他们通过大量扩散歼灭。如果源的密度与应力无关，则遵循9/2幂定律，但蠕变速率明显小于所观察到的蠕变速率。此外，更合理的假设源密度与应力的立方成正比，这导致了3的常规幂律。Spingarn和Nix的模型假定位错滑移并在晶界堆积。这些导致边界上的台阶，这些台阶被晶界扩散所消除。遵循第五次幂定律。原始论文中显示的绝对蠕变率的一致性是由于对表格数据的误读引起的，并且真实的预测蠕变率仍然太低。沿着晶粒内部的位错核心的空位扩散不可能主导晶界扩散，因为位错网络的横截面仅在大晶粒时才超过晶界材料的横截面。尽管Mecking和Estrin已显示即使在位错细胞壁上机械产生的空位浓度也可能仅超过1/2 T_m时才超过热平衡时的空位浓度，但似乎机械产生的高度移动的间隙可能沿着次级滑行系统的位错迁移以使初级系统的空位和间隙偶极子相互抵消，可能的幂定律为5。但是，对安德拉德和汉森的观察可能适用于幂律分解而不是幂律蠕变，强烈表明变形位于晶粒边界。在这种情况下，基于均质变形模型的幂律蠕变理论是不相关的；或者，必须分别处理幂律蠕变和幂律崩溃的制度。

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