铝硅合金中共晶硅的变质机理:杂质诱发共生成对孪晶

为探讨铝硅合金中共晶硅的变质机理,根据杂质诱发共生成对孪晶的理论,对共晶硅的变质机理进行了分析.结果表明:杂质原子诱发的共生成对孪晶之一使得共晶硅在平行于{111}晶面的方向以TPRE的机制生长,而共生成对孪晶中的另一处与原{111}晶面夹角为109.5°的孪晶,则使得共晶硅垂直于{111}晶面方向的生长也按照TPRE机制进行;共生成对孪晶大大加快了共晶硅垂直于{111}晶面方向的生长,并大大降低{111}晶面厚度方向的生长速度与平行于{111}晶面的生长速度的差异,从根本上改变了共晶硅生长时的各向异性特点,使得共晶硅以各向同性方式生长,最终长成纤维状.

Modification mechanism of eutectic silicon in Al-Si alloys: impurity-induced coupled twinning

In order to discuss modification mechanism of eutectic silicon in Al-Si alloys,based on the theory of coupled twinning induced by impurity atom,modification mechanism of eutectic silicon in Al-Si alloys was analyzed.Results indicated that one of the coupled twinnings made eutectic silicon grow parallel to {111} plane by TPRE mechanism,meanwhile the other of the coupled twinnings with an angle of 109.5° to the original {111} plane made eutectic silicon grow perpendicular to {111} plane by TPRE mechanism as well.Thus the coupled twinnings can greatly increase growth speed of eutectic silicon in the direction of vertical to the {111} plane,and greatly reduced the difference between the growth speed vertical to the {111} plane and that parallel to the {111} plane.Therefore the coupled twinning can eliminate anisotropy of eutectic silicon growth on the whole,which leads to the eutectic silicon changes from flake into fiber.