The local deformation and fracture behavior of high-Zn Al-Zn-Mg(-Cu) alloys under hydrogen influence were investigated by in situ tests through synchrotron X-ray tomography. Intergranular and quasi-cleavage fractures were induced by hydrogen, and strain localization by the presence of cracks was not observed by 3D strain mapping. These results suggest that the strain localization at the crack tip is smaller than the measurement limit of 3D strain mapping. The average crack-tip-opening displacements, which are one of the crack driving forces specified by fracture mechanics, directly measured from the tomographic slice were 0.14 and 0.23 μm for intergranular cracks and quasi-cleavage cracks, respectively. The crack driving forces of the intergranular and quasi-cleavage cracks were small. The local deformation behavior at the crack tips was analyzed based on fracture mechanics. The local deformation field of the crack tip, which was characterized using the Rice–Drugan–Sham (RDS) solution rather than the Hutchinson–Rice–Rosengren (HRR) solution, was located within 20 μm of the crack tip, and its size was limited. The results of this work clarify that the intergranular and quasi-cleavage crack growths are caused by small driving forces; however, this behavior is not perfectly brittle, accompanying local deformation at the crack tip.

中文翻译：

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氢影响下高强度铝合金的局部变形和断裂行为

通过同步加速器X射线断层扫描原位测试，研究了高Zn Al-Zn-Mg（-Cu）合金在氢影响下的局部变形和断裂行为。氢引起了晶间和准裂解性断裂，而通过3D应变映射未观察到由于裂纹的存在而引起的应变局部化。这些结果表明，裂纹尖端处的应变局部化小于3D应变映射的测量极限。平均裂纹尖端开口位移，这是裂纹驱动由断裂力学指定力之一，直接从断层切片测得分别为0.14和0.23  μm分别为晶间裂纹和准解理裂纹。晶间和准裂解裂纹的裂纹驱动力较小。基于断裂力学分析了裂纹尖端的局部变形行为。裂纹尖端，使用稻Drugan深水（RDS）溶液而非哈钦森-稻-罗森格伦（HRR）溶液，其特征在于所述的局部变形场，位于20内的 μ裂纹尖端的米，且其大小是有限的。这项工作的结果表明，晶界和准裂解裂纹的增长是由较小的驱动力引起的。然而，这种行为并不十分脆弱，伴有裂纹尖端处的局部变形。