The aim of the present work is to assess in a formal manner “effective” values of the geometrical factor α which takes into account the arrangement of the dislocation pattern in the classical Taylor flow-stress law. For this purpose, selected experimentally well-documented cases of unidirectional and cyclic plastic deformation were analyzed. It is shown that, in both monotonic and cyclic deformation, the α-factor depends on the mode of deformation (single slip versus multiple slip). For examples of dominant primary slip interaction, a value α ≈ 0.1 is found. However, more frequently, α ≈ 0.3–0.4, typical of forest interaction, obtains. As deformation proceeds, the dislocation pattern frequently becomes more heterogeneous (cell formation) and approaches a state of lower energy, with increasing lattice misorientations which arise from an increasing density of geometrically necessary dislocations (GNDs). In these cases, α is generally lowered, for example from an initial value of 0.35 down to values around 0.2. This behaviour is explicable in terms of the composite model in which the heterogeneity is explicitly taken into account. Very similar developments of the dislocation arrangement, accompanied by a decrease of the α-value, are also noted during so-called “steady-state” cyclic and high-temperature creep deformations. In both cases, deformation is shown to be only quasi-stationary due to the fact that well-documented small but non-negligible microstructural changes, associated with a mild increase of the density of the GNDs, persist during deformation. The overall behaviour is readily described in an empirical manner in a unified picture. From the results obtained follows the requirement for a more general flow-stress model which considers explicitly the interaction of different slip systems and the heterogeneity of the dislocation pattern.

本工作的目的是正式评估几何因子α的“有效”值，该值考虑了经典泰勒流应力定律中位错模式的排列。为此，分析了实验记录良好的单向和周期性塑性变形案例。结果表明，在单调变形和循环变形中，α-因子均取决于变形模式（单滑移与多滑移）。对于主导主滑移相互作用的实例中，值α 听，说：0.1中找到。但是，更常见的是，α 获得≈0.3–0.4（典型的森林交互作用）。随着变形的进行，位错图案经常变得更加不均匀（晶胞形成）并接近较低的能量状态，而晶格取向错误则由几何必要位错（GND）的密度增加而引起。在这些情况下，通常将α降低，例如从0.35的初始值降低到0.2左右的值。根据明确考虑了异质性的复合模型，此行为是可解释的。位错排列的发展非常相似，伴随着α的减小在所谓的“稳态”循环和高温蠕变变形过程中也会注意到该值。在这两种情况下，变形都只是准静态的，这是由于事实证明，在变形过程中，微小但不可忽略的微观结构变化（与GND密度的轻度增加相关）仍然存在。整体行为很容易以经验的方式在统一的图片中描述。从获得的结果来看，需要一个更通用的流应力模型，该模型应明确考虑不同滑移系统的相互作用和位错模式的异质性。