Predicting degradation behavior of biodegradable metals in vivo is crucial for the clinical success of medical devices. This paper reports on the effect of long-term static stress on degradation of magnesium alloys and further changes in mechanical integrity. AZ31B (H24) and ZE41A (T5) alloys were tested to evaluate stress corrosion cracking (SCC) in a physiological solution for 30 days and 90 days (ASTM G39 testing standard). Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) and micro-computed tomography (micro-CT) were used to characterize surface morphology and micro-structure of degraded alloys. The results show the different mechanisms of stress corrosion cracking for AZ31B (transgranular stress corrosion cracking, TGSCC) and ZE41A (intergranular stress corrosion cracking, IGSCC). AZ31B was more susceptible to stress corrosion cracking under a long term static load than ZE41A. In conclusion, we observed that long-term static loading accelerated crack propagation, leading to the loss of mechanical integrity.

中文翻译：

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长期静态载荷对基于镁合金的可生物降解金属的降解和机械完整性的研究。

预测体内可生物降解金属的降解行为对于医疗器械的临床成功至关重要。本文报道了长期静态应力对镁合金降解以及机械完整性进一步变化的影响。对AZ31B（H24）和ZE41A（T5）合金进行了测试，以评估其在生理溶液中30天和90天的应力腐蚀开裂（SCC）（ASTM G39测试标准）。扫描电子显微镜（SEM）与能量色散X射线光谱（EDX）和微计算机断层扫描（micro-CT）用于表征降解合金的表面形态和微观结构。结果表明，AZ31B（晶间应力腐蚀开裂，TGSCC）和ZE41A（晶间应力腐蚀开裂，IGSCC）的应力腐蚀开裂的机理不同。AZ31B在长期静态载荷下比ZE41A更容易受到应力腐蚀裂纹的影响。总之，我们观察到长期的静载荷会加速裂纹扩展，从而导致机械完整性的损失。