15 Alternative Composite Design from Recycled Aluminum Chips for Mechanical Pin-Joint (Knuckle) Applications 133 It seems from these graphs, impact resistance is related to absorbed energy. In fact, all of the specimens have shown that the most part of the impact force is used to maintain the balance with the inertia force, and only a small portion of the impact force is actually used to deform and fracture of the specimen. Absorbed energy should be related with the process used here that this energy increases considerably in the structure obtained with sinter+forging. These results are only obtained in laboratory scales and should be improved with detail analyses. 15.3.5 Wear (Scratch) Test Results Reduction of friction rests the key task for wear-resistant composites. Evaluation of the wear resistance of this composite developed in this work have been carried out in two different numbers of cycles, 50*103, and 100*103 cycles. Influence of reinforcement elements and essentially influence of the manufacturing processes, sinter +Forging are observed for three different specimens in the Fig. 15.7 and also wear (scratch) test results were given in Table 15.3 for the specimens of JB, J1 and J2 respectively. The surface damage (mm2), volume lost (μm3) and the depth (μm) values are presented in the same figures for each test condition. Effects of reinforcements and obviously, the effects of the sinter +Forging process are observed as an advantage over others. As shown in the results of scratch tests, the composites processed with sinter+forging has shown always higher wear resistance regarding to the simple structures. In this particular case, the size of the reinforcements and their dispersion on the matrix should have contributed to improve the wear resistance under experimental conditions carried out in the present work. Total evaluations of the microstructure and mechanical properties (static compression, dynamic- drop weight and also wear-scratch tests) give a clear idea about the combined process (sintered+forging). This process applied for these types of composites is caused by bonding diffusion at the interface between matrix and reinforcement and some of the particles were forced into the grains during the forging (second) stage of this process. For this reason, very tough, solid and homogeneous structure could be obtained. Porosity and other structural – micro defects were quasi eliminated. 15.4 Conclusions A novel composite was designed design aluminium matrix composites for the mechanical joints such as the pin – joint very often known as knuckle components as alternative composite against the conventional pieces used for example as rodcouplings, for automotive industries as transmitting pieces. In the frame of this common project, novel composites have been developed from aluminium AA7075 powder obtained with atomization of fresh scrap-chips as the initial form reinforced with B2O3, Mn, Ni, Mg etc. particles as main reinforcements in an economic way. Low cost manufacturing of these composites have been successfully managed through the combined method of sinter +forging. Microstructural analysis has shown that a good bonding at interface of matrix-reinforcement essentially in the specimens manufactured with combined process sinter +forging; a tough and complete microstructure was obtained without porosity. Wear resistance and ductility of these structures should be improved with doping process and good pretreatment conditions; ball milling in longer time is needed for helping the fine and homogeneous distribution of the particles in the matrix. Mechanical behaviour of these specimens produced with sinter +forging process are better than the specimens produced without reinforcement. This process seems very confident values for future work of the production of alternative pieces used in joint parts and also for other tribological applications. Optimizations of the certain parameters such as processing parameters, reinforcement content, etc. need much more experimental work to create real parts in the industrial scales. Here, only limited measurements at room temperature were presented as they are indicative parameters for better understanding the effect of the reinforcements on the optimization of the mechanical, (static and dynamic) and wear properties of the composites produced in the present work. Acknowledgments This work has been carried out on the frame of collaboration between SUPMECA/PARIS and MICHIGAN TECHNICAL UNIVERSITY/ HOUGHTON-MI-USA. Authors acknowledge and appreciate so much Dr. G. ZAMBELIS from Airbus-Helicopter/Paris for valuable technical helps and discussions.
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