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

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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.