Numerical Analysis And Experimental Study On Near Net Shape Forming Of SiC_p/Al Composites Strip By Twin-Roll Cast

SiC_p/Al composites have some superior properties such as high specific strength, low density, reduced thermal expansion coefficient and good conductivity. The properties of SiC_p/Al composites can be altered by change the Si C particle size and its volume fraction. They have a good application prospect in electronic packaging, optical structure element and other domains. Because of the existence of the Si C particles, the composites have worse formability. The forming method which has been widely used is preparing the preform body by stir-casting, spray deposition and so on, firstly, and then forming the expiring shape by forge or hot rolling. To shorten the forming process, a new method was explored, which prepare the composites slurry by stir firstly, and then forming the SiC_p/Al composite strip immediately by twin-roll casting.To explore the preparation procedure of the composites slurry, a VOF model which contains air and aluminum phases was build basing the real stir equipment size. The model was divided in blade zone. The Multiple Reference Frame Model was applied to put various motion state in each zone. The influence of blade shape, blade position and stir velocity to flow field was simulated. Then the stir experiment was conducted to confirm the appropriate stir process parameters. The composite slurry which has good Si C particle dispersion was prepared successfully.To simulate the micro deformation in composites strip during cast rolling, the VPRM(Voronoi Particle Reinforced Model) geometry model which can characterize particle reinforced metal matrix micro-structure was built. The modeling procedure, structural feature and control method of VPRM model was discussed in detail. The materialization of VPRM model by ANSYS APDL was proposed. The VPRM geometry model with different model size, different particle size, different particle volume fraction and various particle gaps was built successfully.The mechanical and thermal properties of SiC_p/Al composites with 20% particle volume fraction and 20μm particle size were obtained by uniaxial compression of VPRM model. The VPRM model was isert into cast rolling strip model to simulate the influence of particle gap distance and particle gap shape on matrix metal deformation in cast rolling process with multiscale analysis. The simulation results show that, when the particle gap distance is 10μm, the matrix metal deform hardly. The larger of gap distance, the weaker of this impede effect. When the particle gap has an angle, the matrix metal deform easier with the angle larger.Basing on the traditional twin-roll casting machine and the composites slurry preparation procedure, the forming techniques feasibility of the SiC_p/Al composites strip by cast rolling was studied and the SiC_p/Al composites strip with 80μm particle size, 4%~12% particle volume fraction, 1~3mm thickness and 50 mm width was prepared. The puddle sample was obtained by rolling stop. Particle distribution in different zones were analyzed by metallurgical microscope. The microscopic observation indicate that the as-cast microstructure is significant in the liquid region. The void in composites slurry decrease and the particle cluster shape change from near spherical to beam during cast rolling. The tensile test and SEM fracture indicate that matrix metal cannot fully permeate into particle cluster zones, which will lead to the weak combine between particles and matrix. Meanwhile, the stress concentration may occurs in particle cluster zones most easier, which will lead the tensile property of composite strip drop down eventually. The SiC_p/Al composite strip with particle uniform distributed was prepared by improve the uniformity of the composites slurry. The mechanical property of the SiC_p/Al composites strip was tested by tensile testing. The results show that, with particle of 80μm size reinforced, the composites strip stiffness improve, but the elongation drop down obviously with the particle volume fraction increase. This is in line with previous research.Furthermore, the casting rolls with groove were prepared, and the near net shape forming techniques of the SiC_p/Al composites strip with special section by cast rolling was explored. It lay the foundations for the further research on this field.