Abstract A systematic investigation based on high-resolution transmission electron microscopy (HRTEM) and quantitative analysis was carried out to gain insights into the structural evolution and deformation behaviors of 57 wt%Cu - 43 wt%Cr dual-phase alloys deformed by high pressure torsion (HPT). Nanometer-sized grains were obtained, with Cu and Cr grain size being reduced from 33.7 nm to 17.4 nm and 35.6 nm to 18.6 nm respectively after deformation with 5 rotations and 25 rotations. During the early deformation stage, in a way, grain refinement in Cu was controlled by the interaction between Cr solutes (or clusters) that was forced to dissolve into Cu matrix and extended dislocations motion. At the higher strain condition, the deformation mode became more complicated and the grain refinement of Cu and Cr can be affected by solute effects and constraint effect during severe plastic deformation in this dual-phase system. In addition, inverse grain-size effect on stacking fault (SF) and twinning tendencies was observed in Cu under different deformation conditions. A critical grain size was calculated to describe the required shear stress for partial dislocation nucleation. HRTEM investigations and statistical analysis on twins observed in 25 rotations-strained sample reveal that the twins are associated with the grain boundary activities and the recovery procedure in the extremely fine grain size region. These atomic-scale observations provide new views in understanding the deformation mode, especially twinning behavior in the extremely fine grain size range below the critical grain size that are hardly obtained in experiments.

中文翻译：

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高压扭转加工的Cu-Cr纳米晶合金的结构演变和变形行为的原子尺度研究

摘要 基于高分辨率透射电子显微镜 (HRTEM) 和定量分析进行了系统研究，以深入了解 57 wt% Cu - 43 wt% Cr 双相合金的高压扭转变形的结构演变和变形行为。 (HPT)。获得纳米尺寸的晶粒，经过5次旋转和25次旋转变形后，Cu和Cr晶粒尺寸分别从33.7 nm减小到17.4 nm和35.6 nm减小到18.6 nm。在变形早期，在某种程度上，Cu 中的晶粒细化是由被迫溶解到 Cu 基体中的 Cr 溶质（或簇）和扩展的位错运动之间的相互作用控制的。在较高应变条件下，该双相体系在剧烈塑性变形过程中，变形模式变得更加复杂，Cu和Cr的晶粒细化会受到溶质效应和约束效应的影响。此外，在不同变形条件下，在 Cu 中观察到逆晶粒尺寸对堆垛层错 (SF) 和孪晶趋势的影响。计算临界晶粒尺寸以描述部分位错成核所需的剪切应力。在 25 次旋转应变样品中观察到的孪晶的 HRTEM 调查和统计分析表明，孪晶与极细晶粒尺寸区域的晶界活动和恢复过程有关。这些原子尺度的观测为理解变形模式提供了新的视角，