Koo Youngmi, Jang Yongseok, Yun Yeoheung
NSF-Engineering Research Center, North Carolina A&T State University, Greensboro, NC 27411, USA. FIT BEST Laboratory, Department of Chemical, Biological, and Bio Engineering, North Carolina A&T State University, Greensboro, NC 27411, USA.
Mater Sci Eng B Solid State Mater Adv Technol. 2017 May;219:45-54. doi: 10.1016/j.mseb.2017.02.009. Epub 2017 Mar 11.
Predicting degradation behavior of biodegradable metals 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.
预测可生物降解金属的降解行为对于医疗设备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的影响以及机械完整性的进一步变化。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）情况（ASTM G39测试标准）。使用带有能量色散X射线光谱仪（EDX）的扫描电子显微镜（SEM）和微计算机断层扫描（micro-CT）来表征降解合金的表面形态和微观结构。结果显示了AZ31B（穿晶应力腐蚀开裂，TGSCC）和ZE41A（沿晶应力腐蚀开裂，IGSCC）应力腐蚀开裂的不同机制。在长期静态载荷下，AZ31B比ZE41A更容易发生应力腐蚀开裂。总之，我们观察到长期静态加载加速了裂纹扩展，导致机械完整性丧失。
