Fabrication And Investigation Of Aluminium Alloy Reinforced With SiC Particulates

The particle reinforced Al matrix composites has many excellent performance, such as high specific strength, specific stiffness, elasticity modulus, abrasive resistance, coeffictent of thermal expansion. Aluminum matrix composites has two kinds of strengthening mechanism.They are the micro mechanism and dislocation mechanism. Dislocation theory is often used for the particle reinforced Al matrix composites. Enhanced phase are added can cause significant changes for metal microstructure, such as the dislocation density increased significantly, matrix grain refinement, the decreases of subgrain size. It also can change the mechanical properties of composite materials.In the article, SiC particulates composites with Al alloy as a matrix were produced by semi-solid stir-casting method. Firstly, structural and mechanical properties of Al alloy, Al-4wt.%SiC and Al-4wt.%oxidized SiC metal matrix composites with percentages of Mg varying from0wt.%to4wt.%in steps of1wt.%was investigated. Secondly, the aging behavior of the composite sample and the unreinforced alloy which take proper heat treatment process was investigated. The solution treatment of the composite sample and the unreinforced alloy was carried out at495℃for1,2and3h.The results and analysis show:1. SiC particulates composites with Al alloy as a matrix were produced by semi-solid stir-casting method. SiC particles distribute are uniform in the matrix alloy. There is no hole was founded on the surface of SiC particles. It was shown that the oxidation of SiC particles can prevent the attack from aluminum molten. When moderate Mg is added in the composites,it can increase the stiffness, yield strength and tensile strength.2. The suitable solution treating time was about2h for both the composite and the unreinforced alloy that led to the fastest aging kinetics and the maximum hardness. The peak hardness of the composite sample took place at shorter times than that of the unreinforced alloy for the samples solution treated for2and3h, but took place at longer times for the samples solution treated for1h.3. At the solution treating time shorter than2h, the aging kinetics decelerated and the hardness values decreased. At the solution treating time longer than2h, the hardness value decreased but no change occurred in the aging kinetics. The difference in age-hardening behavior based on the time of solution treatment has been attributed to the different concentration of solutes in solid solution after the solution treatment. On solution treatment for1h due to incomplete dissolution of precipitates, the concentration of solutes in the solid solution is lower than that on solution treatment for2and3h.