碳化硅颗粒增强铝基复合材料的重熔和铸造工艺特征

Remelting and Casting Process of SiC Particle Reinforced Aluminum Matrix Composites

介绍了SiC颗粒增强铸造铝基复合材料的铸锭重熔、除气和铸造过程的特征。由于颗粒的存在 ,这些工艺过程和普通铝合金有一定的差异。在铸锭重熔时 ,需要控制熔炼温度和对熔体施加搅拌 ,以防止颗粒反应和下沉。普通铝合金采用的熔盐和气体除气工艺不适合于复合熔体的除气精炼 ,而真空除气具有很好的效果。复合熔体具有高的粘度 ,流动性较差 ,在大气自由重力浇注时容易卷入气体而导致铸件气孔缺陷。为了防止铸件缺陷的形成 ,复合材料在大气自由重力浇注下的浇注系统需要设计集气、集渣冒口和阻流口等特殊组元。真空差压浇注工艺大大简化了浇注系统 ,降低了材料消耗 ,同时消除了大气自由重力浇注时容易产生的铸造缺陷。通过该工艺可获得形状复杂、表面光洁。

Remelting, degassing and casting processes of SiC particle reinforced aluminum composites were studied and analyzed. These processes for the composites are somewhat different from those for conventional aluminum alloys due to the existence of SiC particles. During the remelt, the melting temperature is necessary to be well controlled in order to prevent the reaction of Al 4C 3 and it is necessary to stir the composite melt to avoid the particle sink because of the density difference between SiC and aluminum melt. Flux and inert gas degassing processes which are adapted for conventional aluminum alloys are not suitable for the composites. Vacuum degassing is a very effective way for the composites. The composite melts possess higher viscosity and poor fluidity, so bubble defect is usually produced in the composite castings under gravity feed pouring process. To avoid the bubble defect, specific structures including open riser trapping bubbles and inclusions and choke are added in the casting system. A new cast process, vacuum differential pressure casting process is used to produce the composite castings. The construction of casting system for the composites is quite simple in this process, resulting in an obvious material save. Meanwhile, the bubble defect is greatly eliminated, and complicated, thin wall and surface finished composite investment castings are readily obtained by this process.