UDC 621.762 This paper reports the outcome of an investigation into the effect of Al 2 O 3 content on the microstructure and wear properties of Al-Al 2 O 3 metal matrix composites. The Al-Al 2 O 3 composites are prepared by a mechanical alloying method using Al 2 O 3 powders up to 20 vol.% as reinforcement. Alloying is performed in a vibration mill using a ball-to-powder ratio 10:1 and a milling time varying from 30 to 100 min at a rate of 710 Hz. The prepared compositions are cold pressed at 630 MPa with a single action and sintered at 560°C for 30 min under Ar gas atmosphere. The experimental results show that the reinforcing phase Al 2 O 3 is homogeneously dispersed in the Al matrix and the interface between Al matrix and Al 2 O 3 is well formed. Wear tests are carried out under dry sliding conditions using a pin-on-disk testing machine at three different loads of 10, 25, and 50 N and at a sliding speed of 2.08 m/sec. Total sliding distances are selected as 400, 800, 1200, and 1600 m. It is seen that the wear rate decreases with increasing Al 2 O 3 content and sliding distance at a sliding speed of 2.08 m/sec.
INTRODUCTIONMetal-matrix composites (MMCs) containing reinforcement particulates are well known for their high strength, ductility, and wear resistance when compared to their unreinforced counterparts. In MMCs, the ductile structure is provided by the metallic matrix, while the elastic modulus and mechanical strength are increased by the addition of reinforcement phase [1]. The presence of hard reinforcement phases, either particulates, fibers, or whiskers, provides MMCs with good tribological characteristic.Although MMCs are regarded as excellent materials, the high processing costs limit their use. There are a number of processing techniques available for the production of MMCs. Among them, the mechanical alloying (MA), which is a solid-state powder processing technique, has been frequently used to synthesize MMCs with better properties than those obtained by other methods. By using MA technique, the agglomeration of the reinforcement particles is easily prevented and homogeneous distribution of the reinforcement within the matrix is 290 provided [2, 3]. Since MMCs contain at least two materials insoluble in each other, the properties of MMCs can be tailored according to different applications by adjusting the ratio of matrix and reinforcement [4].In recent years, aluminum matrix composites have found extensive application because of their high elastic modulus, hardness, tensile strength at room and high temperatures, and wear properties [5,6]. Although the mechanical properties of particulate-reinforced composites are rather low compared to continuous fiber-reinforced composites, they are preferred by automotive sector due to their low cost and isotropic properties [7,8]. In the automotive applications, SiC-and Al 2 O 3 -reinforced composites are used for the production of cylinder blocks, pistons and break disks [9]. Therefore, the improvement of wear resistance of Al matrix composites is rather impo...
