The fracture behavior of SiCp/A356 composite at room and high temperatures was studied. Under tensile stress condition at room temperature, the fracture is mostly a combination of the brittle fracture of SiC particles...The fracture behavior of SiCp/A356 composite at room and high temperatures was studied. Under tensile stress condition at room temperature, the fracture is mostly a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix. As the tensile temperature increases, the composite changes the main fracture behavior to the separation fracture of the bonding surface between SiC particles and A356 matrix. When the tensile temperature reaches 573 K, the fracture behavior of the composites is almost the whole separation fracture of the bonding surface, which is the main strengthening mechanism at high temperature. Under the cycle stress condition at room and high temperatures, the main fracture behavior of the composites is always a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix. However, under the cycle stress at high temperature, cycle behavior of the composites changes from cycle hardening at room temperature to the cycle softening at high temperature.展开更多
Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the f...Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiCp/A356 composites, and high volume fraction of SiCp with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.展开更多
The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, ...The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, 600 and 610 °C with stirring speeds of 200, 400 and 600 r/min for 10, 20 and 30 min. The distribution of the SiC particles within the matrix, porosity content and tensile properties of the obtained samples were examined. The structural evaluations show that by increasing the stirring time and decreasing the stirring temperature, the uniformity in the particle distribution is improved;however, by increasing the stirring speed the homogeneity firstly increases and then declines. It is also found that by increasing all of the processing parameters, the porosity content is enhanced. From the tensile characteristics viewpoint, the optimum values of the speed, temperature and time are found to be 400 r/min, 590 °C and 30 min, respectively. The contribution of the reinforcement distribution uniformity prevails over that of the porosity level to the tensile properties.展开更多
In order to clarify the dispersion of SiC particles in straight-blade mechanical stirring of A1-SiCp liquid, the dispersion of SiC particles in A356-3.5% SiCp （volume fraction） liquid in a cylindrical crucible was s...In order to clarify the dispersion of SiC particles in straight-blade mechanical stirring of A1-SiCp liquid, the dispersion of SiC particles in A356-3.5% SiCp （volume fraction） liquid in a cylindrical crucible was studied. The relationship between rotating speed of stirrer and radial relative deviation of SiCp content in A356 liquid between the center and the periphery of crucible was established in the conditions of 35° for the gradient angle a of blade and 10 mm/s for the speed of moving up and down of stirrer. The results show that the radial relative deviation of SiCp content increases gradually with increasing the rotating speed of stirrer. When the rotating speed of stirrer is 200 r/min, the vertical dispersion of SiC particles in A356 liquid is even, but the radial relative deviation of SiCp content is 0.24. Consequently, the northomogeneous dispersion of SiC particles in A356 liquid is mainly resulted from the nonhomogeneous radial dispersion of SiC particles.展开更多
基金This work was financiallysupportedbythe National High Technology Research and Development Pro-gram of China(863Program)(No.2003AA331190).
文摘The fracture behavior of SiCp/A356 composite at room and high temperatures was studied. Under tensile stress condition at room temperature, the fracture is mostly a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix. As the tensile temperature increases, the composite changes the main fracture behavior to the separation fracture of the bonding surface between SiC particles and A356 matrix. When the tensile temperature reaches 573 K, the fracture behavior of the composites is almost the whole separation fracture of the bonding surface, which is the main strengthening mechanism at high temperature. Under the cycle stress condition at room and high temperatures, the main fracture behavior of the composites is always a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix. However, under the cycle stress at high temperature, cycle behavior of the composites changes from cycle hardening at room temperature to the cycle softening at high temperature.
基金Project(2007AA03Z119) supported by the National High-tech Research and Development Program of ChinaProjects(2102029,2072012) supported by the Natural Science Foundation of Beijing,China
文摘Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiCp/A356 composites, and high volume fraction of SiCp with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.
文摘The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, 600 and 610 °C with stirring speeds of 200, 400 and 600 r/min for 10, 20 and 30 min. The distribution of the SiC particles within the matrix, porosity content and tensile properties of the obtained samples were examined. The structural evaluations show that by increasing the stirring time and decreasing the stirring temperature, the uniformity in the particle distribution is improved;however, by increasing the stirring speed the homogeneity firstly increases and then declines. It is also found that by increasing all of the processing parameters, the porosity content is enhanced. From the tensile characteristics viewpoint, the optimum values of the speed, temperature and time are found to be 400 r/min, 590 °C and 30 min, respectively. The contribution of the reinforcement distribution uniformity prevails over that of the porosity level to the tensile properties.
基金Project(50974010) supported by the National Natural Science Foundation of ChinaProject(3093023) supported by the Natural Science Foundation of Beijing,ChinaProject(2009JBM091) supported by the Fundamental Research Funds for the Central Universities of China
文摘In order to clarify the dispersion of SiC particles in straight-blade mechanical stirring of A1-SiCp liquid, the dispersion of SiC particles in A356-3.5% SiCp （volume fraction） liquid in a cylindrical crucible was studied. The relationship between rotating speed of stirrer and radial relative deviation of SiCp content in A356 liquid between the center and the periphery of crucible was established in the conditions of 35° for the gradient angle a of blade and 10 mm/s for the speed of moving up and down of stirrer. The results show that the radial relative deviation of SiCp content increases gradually with increasing the rotating speed of stirrer. When the rotating speed of stirrer is 200 r/min, the vertical dispersion of SiC particles in A356 liquid is even, but the radial relative deviation of SiCp content is 0.24. Consequently, the northomogeneous dispersion of SiC particles in A356 liquid is mainly resulted from the nonhomogeneous radial dispersion of SiC particles.
