Researches On Preparation Of SiCp/Al Surface Composite

Aluminum alloy has good plasticity, toughness and high ductility, but its low hardness and poor wear resistance limits its application in automobile and aerospace. Particles reinforced aluminum matrix composite materials can improve the hardness and wear resistance of composite materials, but the addition of ceramic particles also reduced the aluminum alloy plasticity, toughness and ductility. In the practical application of aluminum alloy, friction and wear mainly occurred on the surface of materials, so the way of ceramic particles were added only to the surface layers was adopted. Particles reinforced aluminum matrix composite materials with high wear resistance, good ductility and toughness was produced. In order to explore a new method to prepare SiC particles reinforced surface composite layer of aluminum alloy, the friction stir processing, laser+friction stir processing, laser-TIG+friction stir processing, TIG+friction stir processing were used.In this paper, micro-sized SiC particles were selected as reinforcements, and the 6061 aluminum alloy was selected as the matrix material. SiC particles reinforced surface composite layer of aluminum alloy were prepared via four kinds of methods, the surface composite layer microstructure, phase composition, phase distribution and hardness analysis were studied. The microstructures, phases, particles distribution and micro-hardness were systematically investigated.The friction stir processing of 6 mm thick 6061 aluminum alloy was studied, and the best processing parameters were 950 rpm of rotation speed,30 mm/min of traverse speed and 0.25mm of shoulder insertion. Among which phase in the surface layer of composite material was uniformly distributed by 6-pass FSP. However, associative property between matrix and SiC was poor.Smaller size and needle brittle Al4C3 phase was generated during the small energy laser cladding, Al4C3 and larger size and needle brittle Al4SiC4 phases were generated during great energy laser-TIG and TIG cladding. Friction stir processing can not only eliminate the original holes in the aluminum alloy and welding porosity defect, but also can break Al4C3, Al4SiC4, silicon block and smooth the sharp-angled part. Friction stir processing also can uniformly mixed the broken phase with SiC in the cladding layer, and obtained the cladding layer with fine-grained and no obvious defects on the surface.Phase in the surface layer of composites has a small amount of agglomeration prepared by laser+2-pass FSP. Phase in the surface layer of composites was uniform, no obvious agglomeration prepared by laser-TIG+6-pass FSP and TIG+6-pass FSP. The surface layer of composites prepared by two methods has no obvious difference. Compared with base metal, the microhardness of cladding layer by three methods increased about 22% and showed a W-shaped distribution.