Fatigue behavior of aluminum-matrix-composites (AMC) in the range of high number of cycles

传统材料越来越多地达到了要求轻质结构的极限。为解决这一问题，近年来铝基复合材料应运而生。AMC是一种轻质复合材料，与添加小颗粒高强度陶瓷颗粒实现的母材相比，具有更好的力学性能。但到目前为止，关于AMCs力学性能的科学验证研究还很少，因此这一创新材料群的应用领域很少。AMC的可持续应用将特别在交通工程中看到。因此，除了单调性质外，这些材料的疲劳行为也备受关注。使用创新的测试设备，如材料科学与工程研究所(WKK)开发的超声波检测设备，可以在30分钟内实现107次加载循环。在最近的研究项目范围内，研究了选定的AMC和铝基材料在105-109个载荷循环范围内的循环变形行为。更新项目的中心目标之一是系统地扩展先前获得的关于AMC疲劳行为的知识，用于超声检测系统适用的载荷循环范围。为了描述颗粒体积分数作为影响AMC力学性能的主要参数的效果，必须系统地改变颗粒体积分数。现有的高分辨率测量方法，如温度测量和电阻值记录，仍将用于分析和描述微观结构变化。更新项目的另一个中心问题是载荷比的变化，因为特别是对于颗粒增强金属基复合材料，平均载荷对疲劳行为和裂纹萌生的影响是相当大的。此外，还应将超声波检测设备获得的结果与在伺服液压测试系统上进行的25赫兹测试进行比较，以阐明测试频率的可能影响。最后，将进行光学和扫描电子显微镜研究以及能量色散X射线(EDX)、残余应力测量(XRD)和2D显微硬度图，以表征微观结构和失效机理。此外，微型计算机断层扫描将用于确定金属夹杂物作为制造过程的残留物。

Conventional materials reach more and more their limits for demanding light weight constructions. To solve this problem aluminum-matrix-composites (AMCs) have been developed over the past years. AMCs are light weight composites with better mechanical properties in comparison to the matrix material realized by the addition of small high strength ceramic particles. But until now, only a few scientific validated studies concerning the mechanical properties of AMCs are available, so there are only minor application fields for this innovative material group. Sustainable applications for AMCs will be seen in particular in traffic engineering. Hence beside monotonic properties especially the fatigue behavior of these materials is of high interest. Using innovative testing equipment like the ultrasonic testing facility developed at the Institute of Materials Science and Engineering (WKK), load cycles of 107 can be realized within 30 minutes. Within the scope of the recent research project the cyclic deformation behavior of selected AMCs and the aluminum base material was investigated in the range of 105 to 109 load cycles.One central aim of the renewal project is a systematic extension of the previously attained knowledge of the fatigue behavior of AMCs in the for ultrasonic testing systems suitable load cycle range. To describe the effect of the particle volume fraction as a main influence parameter of the mechanical properties of AMCs, the particle fraction should be systematically varied. The established high-resolution measuring methods such as temperature measurements and recording of electrical resistance values will be still used to analyze and describe the microstructural changes. A further central issue of the renewal project is the variation of the load ratio, because especially for particle reinforced metal matrix composite a considerable influence of the mean load on the fatigue behavior and the crack initiation can be expected. Furthermore the results obtained using the ultrasonic testing facility should be compared with investigations carried out with 25 Hz on a servo-hydraulic testing system to clarify a possible influence of the testing frequency.Finally, light- and scanning electron microscopy investigations as well as energy-dispersive x-ray (EDX), residual stress measurements (XRD) and 2D-microhardness mappings will be carried out to characterize the microstructure and the failure mechanism. Additionally, micro-computer tomography scans will be used to determine metallic inclusions as residue of the manufacturing process.