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Composite Powders

Aluminium Matrix Composites - Effects of Powder Compositing on SiC Distribution

In this study, SiC-Al composite powder was fabricated by high-energy ball milling. Then it was stirred into molten aluminum to obtain particle reinforced aluminium matrix composites (AMCs) with SiC weight fractions of 0.5%, 1.0% and 1.5%. Effects of milling times on morphology, crystal size and SiC inlaid ratio of composite powders were invesgated. The tensile strength and Vickers-hardness of these AMCs turned out to be higher than the ones of unreinforced aluminum by 46.8%, 63.8%, 34.0% and 99.1%, 116.1%, 67.9%. At the same SiC additional ratio, the AMCs reinforced with composite powder had higher tensile strength and Vickers-hardness than the AMCs reinforced with pure SiC powder by 26.0% and 38.2% and had more homogenous SiC distribution, which means that SiC particles are more easily dispersed into molten aluminum after compositing with Al particles.
Key words: Aluminum matrix composites (AMCs); mechanical dispersion; high-energy ball milling; stir casting
SiC particle reinforced aluminum matrix composites (AMCs) have outstanding qualities such as high specific tenacity, high specific stiffness, high thermal conductivity and low coefficient of thermal expansion. They can be reworked by conventional process equipments, and the cost of processing is low. Therefore AMCs have been frequently studied during recent 30 years and become one of the most promising materials [1~3]. Presently, powder metallurgy, stir casting, spraying deposition and infiltration are mainly used in AMCs preparation [4]. There are some differences in distributing homogeneity and interface situation between composites prepared by different methods. In these methods, stir casting is most popular because of its low costing and manipulating simpleness. So far, stir casting has been widely used in aviation field, car industry, manufacturing of machines and sports equipments[5].
In this work, SiCp-Al composites were firstly prepared by ball milling and stir casting: SiC particles and Al particles were composited by high-energy ball milling the purpose of which was to make small size SiC particles embed into big size Al particles [6]. Then the composite powder was added into molten aluminum to obtain SiCp-Al composites. By this method, we resolved the problems of interface and wettability which were common in conventional stir casting method.