Wear characteristics of surface-hybrid-MMCs layer fabricated on aluminum plate by friction stir processing

Aluminum-base hybrid composites reinforced with mixtures of SiC and Al2O3 particles 1.25 mu m in average size have been fabricated on an A 1050-H24 aluminum plate by friction stir processing (FSP) and their wear resistance has been investigated as a function of relative weight ratios of the particles. A mixture of SiC and Al2O3 powders of different weight ratios was packed into a groove of 3 mm width and 1.5 mm depth cut on the aluminum plate, and covered with an aluminum sheet 2 mm thick. A FSP tool of square probe shape, rotated at a speed of 1500 rpm, was plunged into the plate through the cover sheet and the groove, and moved along the groove at a travelling speed of 1.66 mm/s. After the hybrid composite was fabricated on the Al plate, the homogeneity of the particles distribution inside the Al matrix has been evaluated from the macro/microstructure and hardness distribution. Moreover, the wear characteristics of the resulted hybrid composites were evaluated using a ball-on-disc wear tester at room temperatures at normal loads of 2, 5, and ION. As a result, it was found that the reinforcement particles were distributed homogenously inside the nugget zone without any defects except some voids that appeared around the Al2O3 particles. The average hardness decreased with increasing the relative content of Al2O3 particles. Regarding the wear characteristics, the wear volume losses of the hybrid composites depended on the applied load and the relative ratio of SiC and Al2O3 particles. The hybrid composite of 80% SiC + 20% Al2O3 showed superior wear resistance to 100% SiC and Al2O3 or any other hybrid ratios at a normal load of 5 N, while the wear resistance was insensitive to the reinforcement ceramic type and was very close to the unreinforced FSP sample at a normal load of ION. (c) 2010 Elsevier B.V. All rights reserved.