Production of AlMg3/SiCp composites and investigations of variations in mechanical properties

ABSTRACT In space, aviation, automotive and defence industries, light machinery parts and structure components with high erosion resistance and specific strength are demanded. In such engineering applications that are easy, economic and intended to be produced within the minimum completing processes for predetermined physical properties, metal matrix composites are being used at an increasing rate. In the forming operation, retaining the qualities obtained in the manufacturing process is still among the major problems for the manufacturers and producers to overcome. The use of discontinuous reinforced aluminum composites are accepted as a potential solution to the aforementioned problem. The intention of this study is to manufacture particle reinforced aluminum matrix composite materials and investigate the effects of varied volume fractions of SiC and cold rolling on the mechanical and microstructural properties of these materials. This study was carried out at two steps. At the first one, particle reinforced aluminum matrix composites were manufactured by modified compocasting and squeeze casting methods at variable reinforced volume fraction. The second step composite materials were cold rolled at varying reductions. In order to reduce such problems of stirring which were caused by poor wettability of reinforced phases by matrix materials in casting operation at the composite material manufacturing, non-homogeneous stirring of the reinforced matrix material homogeneously and undesired rejection of the reinforcement; melt stirring and semi-solid stirring processes were modified and by reinforcing composite materials at high volume fractions homogeneous stirring of the material was maintained. The problems encountered during the stirring process were solved by the use of stirrers designed specifically for variable temperature ranges. Furthermore, the processes are carried out at the lowest temperature possible in order to minimize undesired interface reactions. At the proceeding step, variably reinforced composite materials were cold rolled at varying reductions. Microstructural and mechanical properties of the obtained composite materials were determined. Consequently, the use of modified technique improved the wettability of SiC, prevented rejection of the reinforcement in the stirring process and the clusters problems and maintained homogenity. By employing the squeeze casting method after semi-solid stirring, a relatively low level of porosity was obtained in comparison to other casting methods. The rolling process and the increase in reinforced volume fraction affected the cold formability of the composite materials and decreased elongation, however the estimated increase in tensile strength, yield stress, elasticity modulus and hardness was observed. Keywords: Metal matrix composites, rolling, aluminum, SiC, squeeze casting, semi solid stirring