SiCp/Al复合材料搅拌铸造新型搅拌器流场及工艺研究

SiCp/Al复合材料搅拌铸造法虽然具有制备成本低、近终成型的优点,但是实现SiC颗粒在铝合金熔体的均匀分散难度很大,这与搅拌器结构及搅拌工艺有直接关系。采用数值模拟和实验相结合的方法开展了新型桨栅复合搅拌器设计及其工艺研究,比较了桨栅复合搅拌器与单一搅拌器的流场结构和速度场分布,并在此基础上进行了搅拌铸造工艺研究。结果表明:(1)桨栅复合搅拌器能够较好地实现复合材料大体积熔体的均匀搅拌和高速剪切,复合搅拌器内熔体的流场为较好的轴向和径向循环,液面更为平稳,搅拌转速500r/min时熔体最大速度为3.9m/s,流场结构和剪切速度均优于单一形式搅拌器;(2)用桨栅复合搅拌器进行20%(质量分数)SiCp/A357复合材料搅拌铸造工艺实验,在搅拌温度610℃、搅拌转速500r/min、搅拌时间20min的工艺条件下,SiC颗粒分布均匀且无气孔缺陷。

Study on Flow Field and Process of New Stirrer for Stir Casting of SiCp/Al Composites

Preparing SiCp/Al composites by stir casting process has the advantage of low cost and near-net shape.However,it is difficult to make SiC particles uniformly distribute in Al alloys,which is strongly dependent on the stirrer configuration and its casting process.In this study,a new paddle-grid compound stirrer was investigated to achieve powerful and uniform stirring by numerical and experimental methods.The velocity and flow field of the paddle-grid compound stirrer and the single stirrers were numerically compared,and then the optimal stir process using paddle-grid compound stirrer was experimentally done.The results showed that more uniform stir and more intense shear in large volume slurry could be achieved for the paddle-grid compound stirrer than the single stirrers.The flow field of paddle-grid compound stirrer was axial and radial circulation and the liquid level was smooth.The maximal fluid velocity was 3.9 m/s with the rotating speed of 500 r/min.The SiCp uniform distribution without pore was obtained in the production of 20wt％SiCp/A357 composites at the conditions of the optimal process parameters of stir temperature 610 C,stir speed 500 r/min and stir time 20 min.