| The novel (Al2O3+Al3Zr)p/Al-22Si matrix composites are prepared via in-situ melt reaction from (Al-22Si)-Zr(CO3)2. The solidification microstructure, in-situ Particulate features, mechanical properties and friction wear properties of the as-prepared composites have been investigated by using Optical Microscope (OM), Scanning Electron Microscope (SEM), Electron Probe Microanalyzer (EPMA), X-ray Diffractorneter(XRI)) and other modern equipment. The natures and mechanism of these characteristics have been analyzed.Experimental results show that the primary silicium, Al2O3 and Al3Zr reinforcement particulates have been obtained in the as-prepared composites. The average size of the primary silicium is about 20～25μm, Al2O3 and Al3Zr reinforcement particulates are nearly uniformly distributed in the matrix, and the average size is about 1-3μm. The results of metallographic analysis show that the volume friction of the primary silicium in Al-22Si is about 22.87%, is above its theoretical value; the volume friction of (Al2O3+Al3Zr)/Al-22Si can be to 34.1%..The optimization parameters for the fabrication of (Al2O3+Al3Zr)p/Al-22Si composites are the following: the reaction time is 30min; the initial reaction temperature is 850℃, the additional mass of Zr(CO3)2 is 20% to the total of the aluminum molten. The shapes and the sizes of primary silicon, Al2O3 and Al3Zr are refined with the cooling rate increasing.Mechanical property tests show that the tensile strength and hardness(as-anneal) of (Al2O3+Al3Zr)p/Al-22Si composites are higher than that of its matrix alloy, respectively, and increased with the increase of the volume fraction, but the elongation decreased. With the 11.2vol% in-situ paniculate, the values forσb and HB increased by 49.3% and 35.2% to the Al-22Si, reach 230.4MPa and 96, respectively. The morphologies for the fracture surface of the composites show that the fracture mechanism is brittle fracture.Dry sliding wear tests at room temperature show that the wear resistance of the composites is superior to that of its matrix alloy; the friction coefficient reduced with the load increasing; the friction coefficient of the composite decreased with the increase of the volume fraction of the reinforcement particles. The friction coefficient of the composites is more stability than that of the matrix alloy. The wear mechanisms of the composites determined by the SEM microstructures of the wear surface, subsurface and wear debris show that the wear mechanism of the composites is adherence wear and abrasion wear. With the same load, the wear mechanism transformes from adherence wear and abrasion wear to abrasion wear with the increase of the volume fraction of the particles. With the same volume fraction of the particles, the the wear mechanism transformes from abrasion wear to adherence wear and abrasion wear with the increase of the load.Dry sliding wear tests at high-temperature indicate that the wear weight loss of the composites increased with increase of the load, and the friction coefficient reduced. With the increase of the temperature, the wear weight loss of the composites decreased, and the friction coefficient reduced firstly and then increased. The SEM of the wear surface indicates that the wear mechanism transforme from adherence wear and abrasion wear to adherence wear.The results of thermal expansion of composites show that, compared with Al-22Si matrix, the liner expansibility of composites decrease obviously, and with the increase of the volume fraction of particles, the linear expansibility of composites decrease in the temperature 20-300℃, but with the increase of temperature, the linear expansibility of composites increase with the same particle volume. With the comparison between the practical value and theoretical valun, the practical is more near to the model of Kerner and Turner.
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