Al-5Ti-B细化剂对A356合金微观组织的影响

制定合理的熔炼工艺熔配A356合金,并在浇注前加入不同含量的Al-5Ti-B细化剂对合金液进行细化处理,研究细化剂对A356合金组织和性能的影响.研究结果表明:加入Al-5Ti-B能使A356合金中的初生α-Al相显著细化,该相由粗大的树枝晶变为细小、无定向的枝晶;由于晶粒变小晶界增多,硅相变得更为分散地分布在枝晶和晶粒间隙内,导致粗大的针片状共晶硅减少且长度变短,使应力集中程度降低.当细化剂加入量在1.0%时细化效果最好,二次枝晶间距为22.98μm,铸态下其硬度为62.4HB,而不经过细化处理的A356合金,其硬度仅为52.0HB,相比提高了12.4%.

The effect of Al-5Ti-B refiner microstrueture of A356 alloy

The author formulate a reasonable process of A356 alloy. And a series of different amounts of Al-5Ti-B grain refiner have been added into the mdten before pouring, to investigate the effect of Al-5Ti-B grain refiner on micstructure and mechanical properties of A356 alloy. The results show that the primary α-Al phase in A356 alloy can be refined significantly, which are changed into fine non-directional dendrites from coarse dendrite. Meanwhile, due to the decrease of grain size, grain boundary increase a lot,silicon phase change more dispersed and the size of eutectic silicon in the alloy is decreased. As a result, the stress concentration level is reduced. The desirable refinement of the α-Al phase in A356 alloy is obtained with 1.0% Al-5Ti-B refiner, the mechancial properties of as-cast A356 with 1.0% Al-5Ti-B refiner reach 62.4 HB in hardness.