Current surface mechanical treatment techniques that produce gradient microstructures and return a combination of high strength and high uniform elongation are limited in terms of their industrial suitability. This study applies a modified surface rolling strategy, namely accumulative skin pass rolling (ASPR), to produce a gradient microstructure in copper and return an increase in yield strength while preserving high uniform elongation. Uniaxial tension combined with in-situ electron back-scattering diffraction compared the variations in mechanical properties and microstructure after annealing and ASPR. The increase in yield strength after ASPR is ascribed to the higher dislocation density at subgrain and grain boundaries, junctions and interiors whereas the preservation of uniform elongation is due to the gradient microstructure comprising a range of grain sizes across the sheet thickness. Finite element analysis of ASPR samples revealed strain heterogeneity along the gauge length and a transfer of load from softer grains in the sheet interior to harder grains closer to the sheet surface during tension. The results indicate that ASPR may be a promising new strategy for the continuous fabrication of sheets with gradient microstructures.

当前产生梯度微结构并返回高强度和高均匀伸长率组合的表面机械处理技术在其工业适用性方面受到限制。本研究采用改进的表面轧制策略，即累积表面光轧 (ASPR)，在铜中产生梯度微观结构，并在保持高均匀伸长率的同时提高屈服强度。单轴拉伸结合原位电子背散射衍射比较了退火和 ASPR 后机械性能和微观结构的变化。ASPR 后屈服强度的增加归因于亚晶界和晶界、结点和内部更高的位错密度，而均匀伸长率的保持是由于梯度微观结构包括整个板材厚度的一系列晶粒尺寸。ASPR 样品的有限元分析揭示了沿标距长度的应变不均匀性，以及在张力期间载荷从板材内部较软的晶粒转移到更靠近板材表面的较硬晶粒。结果表明，ASPR 可能是连续制造具有梯度微结构的板材的一种有前途的新策略。