Abstract Damage accumulation is studied in a rolled, partially annealed magnesium alloy by means of synchrotron tomography. To avoid failure by plastic instability and generate an effective damage process zone, round notched bars are deformed up to crack initiation then sheet-like samples are cut out for subsequent tomography observations. The effect of the hydrostatic stress is explored by considering two notch radii. In a given specimen, advantage is taken of the naturally occurring gradients in plastic strain and stress triaxiality to gain insight into the various stages of damage progression, damage-to-fracture transition, as well as crack propagation. The key finding is that damage is quite diffuse in both types of specimens. The observations document extensive void nucleation, growth and coalescence, reminiscent of the most ductile and tough metallic materials. Crack growth is found to be inherently anisotropic. Crack initiation is found to occur predominately at the center of the specimen with a blunt notch, and near the notch root in the specimen with a sharp notch. Quantitative measurements based on about 1000 microvoids and blunted microcracks enable values of void volume fraction and microcrack blunting to be fairly estimated, at macroscopic crack initiation.

中文翻译：

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通过同步辐射层析成像研究镁合金中的空隙生长和聚结

摘要 通过同步辐射断层扫描技术研究了轧制、部分退火的镁合金的损伤累积。为了避免塑性不稳定性导致的失效并产生有效的损伤过程区，圆形缺口棒变形直至裂纹萌生，然后切下片状样品用于后续断层扫描观察。通过考虑两个缺口半径来探索静水应力的影响。在给定的试样中，利用塑性应变和应力三轴性中自然发生的梯度来深入了解损伤进展、损伤到断裂转变以及裂纹扩展的各个阶段。关键的发现是，两种类型的标本的损伤都相当分散。观察记录了广泛的空隙成核、生长和聚结，让人想起最具延展性和韧性的金属材料。发现裂纹增长本质上是各向异性的。发现裂纹萌生主要发生在带有钝缺口的试样的中心，以及带有尖锐缺口的试样的缺口根部附近。基于约 1000 个微孔洞和钝化微裂纹的定量测量能够在宏观裂纹萌生时公平估计空隙体积分数和微裂纹钝化的值。