Research On Gas-free Stir Casting Of SiCp/Al Composite

SiCp/Al composites are widely used in aerospace,transportation,electronic packaging and other fields owing to their excellent properties.Among the preparation methods of SiCp/Al composites,semi-solid stir casting is the more economic method which has low production cost and can easily realize near-net forming.These problems of gas entrapment and inhomogeneous distribution of SiCp in matrix obviously exist in semi-solid stir casting of SiCp/Al composites.In this paper,numerical simulation and experiment were used in the gas-free stir casting research of SiCp/Al composites.Gas entrapment was avoided effectively and the uniform distribution of SiCp was realized.Then the tensile properties of SiCp/Al composites were tested.The main contents were as follows:The effects of horizontal angle ? of crucible blade and stirring time t on the distribution of SiCp were studied by computational fluid dynamics(Computational Fluid Dynamics,CFD)numerical simulation method.Horizontal angle ? of blade which could make SiCp evenly distributed was ?=30°,and the reasonable stirring time was more than 300 s.These simulated results provided reliable guidance and reference for subsequent experiments.The semi-solid slurry was prepared using electromagnetic mechanical stirring equipment developed by our team.Gas entrapment could be completely avoided,and porosity of composite could be reduced from about 3.08 vol.%to 0.04 vol.%.The simulated stirring conditions were verified.The relationship between solid fraction fs and stirring temperature T was established.The conventional casting of SiCp/Al semi-solid slurry was carried out.The technical condition which could restrain the deposition of SiCp was fs? 20%.The homogeneous SiCp/Al composite was obtained.For Al matrix without porosity obtained in this study,compared with Al matrix with porosity,its yield strength was increased from 63 MPa to 66 MPa,and its tensile strength was increased from 113 MPa to 131 MPa.With the increase of SiCp content,yield strength and tensile strength of homogeneous SiCp/Al composite without gas entrapment were gradually increased,but elongation was gradually decreased.When the SiCp content was 4 vol.%,yield strength could be increased to 108 MPa,tensile strength could be enhanced to 211 MPa and elongation could be 10.5%.This SiCp/Al composite possessed not only high strength but also good plasticity.Therefore the ideal SiCp content was 4 vol.%.The reasonable processing conditions of the gas-free and homogeneous SiCp/Al composite were obtained in this study.It can be seen that a new way for the SiCp/Al composite with high performance is explored.