单晶易滑移阶段位错结构形成的动力学分析

DYNAMICAL ANALYSIS ON THE FORMATION OF DISLOCATION PATTERN IN THE EASY SLIP STAGE OF SINGLE CRYSTALS 1

提出了偶极子的保守攀移机制，并建立了一个新的单滑移位错动力学模型，应用该模型揭示了单晶硬化Ⅰ阶段（易滑移阶段）一种平面列阵结构———地毯（ｃａｒｐｅｔｓ）结构的形成，与实验吻合．该模型的特点是计及了偶极子的滑移和攀移机制；正、负可动位错的滑移、攀移、交滑移引起的位错线的三维运动以及位错的增殖和反应．线性稳定性分析和非线性分叉分析表明：位错花样（ｐａｔｔｅｒｎ）的形成是初始统计均匀分布位错系统在外力驱使下远离平衡态后产生动力学失稳形成的一种稳定结构．研究还揭示了地毯结构形成导致宏观硬化减少，易滑移阶段出现的本质．

The mechanism governing the conservative climb of dipoles and a new dislocation dynamic model for single slip are proposed. Using this model, the formation of the carpet that is a planar array structure in the I stage of crystal hardening is predicted, in agreement with the experimental results. The present model takes into account not only the drift and climb mechanism of dipoles but also the three-dimensional movement of plus and mines mobile dislocations through slipping and cross-slipping. Besides, the multiplication and reaction of the dislocation species are considered in a different way from the previous studies of the subject. Linear stability and non-linear bifurcation analyses show that dislocation patterns correspond to the stable structure formed with the dynamic instability of statistically homogeneous dislocation distribution driven far from equilibrium state.The critical conditions are given, corresponding to Hopf bifurcation and Turing instability, respectively. Also, the analytical form of the dislocation pattern near the singular point is yielded. Applying Orowan's formula, the correlation between the carpet structure and the easy slip behavior in stage I of the hardening is clarified in the present study. It is shown that although the total dislocation densities remain unchanged just after dislocation pattern appears, the hardening of crystals begins to decrease. This result demonstrates that the effect of dislocation patterns on the hardening is more essential than dislocation density itself. Finally, the reason why there are longer hardening stages I for alloy crystals and the crystals irradiated with neutrons is discussed.