Shasha Yao

Radial Distribution of SiC Particles in Mechanical Stirring of A356–SiCp Liquid

The mechanical stirring of A356–2.5 vol.% SiC p liquid was conducted in a cylindrical crucible by a straight-blade stirrer. The radial distribution of SiC particles in A356 liquid was studied under the conditions of 25 deg. for gradient angle α of blade and 10 mm/s for speed of moving up and down of stirrer. The results show that there exists a nonlinear relationship between rotating speed of stirrer and radial relative deviation of SiC p content in A356 liquid between the center and the periphery of crucible. The greater the rotating speed of stirrer is, the bigger the radial relative deviation of SiC p content in A356 liquid becomes and the more nonhomogeneous the radial distribution of SiC particles in A356 liquid turns. In addition, when the rotating speed of stirrer is about 200 r/min, the vertical distribution of SiC particles in A356 liquid is relative uniform. It can be seen that the nonhomogeneous distribution of SiC particles in A356 liquid results from the nonhomogeneous radial distribution of SiC particles in A356 liquid in straight-blade mechanical stirring ultimately.

The Uniform Distribution of SiC Particles in an A356-SiCp Composite Produced by the Tilt-blade Mechanical Stirring

The tilt-blade mechanical stirring of A356-2.5vol.%SiCp liquid was conducted in a cylindrical crucible to solve the problem of nonhomogeneous radial distribution of SiC particles in conventional straight-blade mechanical stirring. The radial distribution of SiC particles in A356 liquid was studied under the conditions of 25° for horizontal tilt angle α of the blade, 200 r/min for rotating speed of stirrer and 10 mm/s for speed of moving up and down of stirrer. The results show that there exists a nonlinear relationship between circumferential tilt angle β of the blade and radial relative deviation d of SiCp content in A356 liquid. When β is smaller than 26°, the d of SiCp content in A356 liquid between the center and the periphery of crucible decreases with increasing β. Conversely, when β is bigger than 26°, d increases with increasing β. Only when β is about 26°, d can be equal to nought i.e. uniform radial distribution of SiC particles can be realized. It can be seen that the nonhomogeneous radial distribution of SiC particles in conventional straight-blade mechanical stirring can be eliminated in this tilt-blade mechanical stirring of A356-SiCp liquid.