Abstract Severe plastic deformation imposed under high hydrostatic pressure introduces a considerable dislocation substructure in metals from the early stages of deformation, ultimately resulting in grain fragmentation. Characterization and quantification of the substructure require methods with a sufficiently high angular and spatial resolution to reveal the local heterogeneities in orientation differences and the length scales of the substructure. However, the statistical relevance of the observations should be assured which requires relatively large fields of view. In present work, the evolution of dislocation substructures during static and dynamic high pressure torsion processing of commercially pure aluminum is examined. Orientation data obtained by electron backscatter diffraction using two different mapping step sizes are utilized to assess the detection of the dislocation substructures and boundaries during the grain fragmentation stage. Accumulation of distortion in the crystal produces an increase in measurement noise at each pixel which is estimated using Kamaya's plots. The storage of dislocations and related angular misfits reduces the peak height of the probability density distribution of misorientation gradients, moves the peak to higher misorientation gradients and widens the distribution. Superposition of double Rayleigh distributions over the combined dislocation boundary data predicts a slightly higher median for the frequency of geometrically necessary boundaries and larger misorientation gradients across these boundaries in dynamically deformed material. In incidental dislocation boundaries, higher misorientation gradients are only observed at lower equivalent strains. Buildup of shear strain leads to the deterioration in the quality of the fitting to a double Rayleigh distribution and is linked to the complex evolution pattern of the dislocation boundaries. Finally, in statically deformed material, anisotropy in the substructure evolution is observed in the shear and radial planes.

中文翻译：

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静态和动态高压扭力作用下商用纯铝位错子结构的统计分析

摘要 在高静水压力下施加的剧烈塑性变形从变形的早期阶段就在金属中引入了​​相当大的位错亚结构，最终导致晶粒破碎。子结构的表征和量化需要具有足够高的角度和空间分辨率的方法，以揭示方向差异和子结构长度尺度的局部异质性。然而，应确保观察的统计相关性，这需要相对较大的视场。在目前的工作中，研究了商业纯铝在静态和动态高压扭转加工过程中位错子结构的演变。使用两种不同的映射步长通过电子背散射衍射获得的方向数据用于评估在晶粒破碎阶段对位错子结构和边界的检测。晶体中失真的累积会导致每个像素的测量噪声增加，这是使用 Kamaya 的图估计的。位错和相关角度失配的存储降低了取向差梯度的概率密度分布的峰高，将峰移动到更高的取向差梯度并加宽了分布。双瑞利分布在组合位错边界数据上的叠加预测几何必要边界频率的中值略高，动态变形材料中跨越这些边界的取向差梯度更大。在偶然的位错边界中，只有在较低的等效应变下才能观察到较高的取向差梯度。剪切应变的积累导致双瑞利分布的拟合质量下降，并与位错边界的复杂演化模式有关。最后，在静态变形材料中，在剪切平面和径向平面中观察到子结构演化的各向异性。剪切应变的积累导致双瑞利分布的拟合质量下降，并与位错边界的复杂演化模式有关。最后，在静态变形材料中，在剪切平面和径向平面中观察到子结构演化的各向异性。剪切应变的积累导致双瑞利分布的拟合质量下降，并与位错边界的复杂演化模式有关。最后，在静态变形材料中，在剪切平面和径向平面中观察到子结构演化的各向异性。