Al-Si 共晶系连续定向凝固自生复合材料的组织与性能

THE STRUCTURE AND PROPERTIES OF CONTINUOUS DIRECTIONAL SOLIDIFICATION Al-Si EUTECTIC IN SITU COMPOSITES

本文采用新型连续定向凝固(CDS)装置研究了 Al-Si 合金(成分为12.7%～16.6%Si)的可采用工艺范围、共生区及其连续定向凝固材料的组织与性能。实验结果表明,Al-Si 共晶系合金通过连续定向凝固可以获得短纤维的自生复合材料.在凝固速度为0.02～2.0mm/s 的范围内,随着凝固速度的增加,Al-Si 共晶系合金的共晶硅形态经历了片/纤维转变,抗拉强度及延伸率随凝固速度的增加而增大。本文还分析了 Si 纤维的形成机制。

In this paper,the adoptable rangees of process parameters,the coupled zone,the structure and properties of eutectic and hypereutectic Al-Si alloys (Al-12.7-16.6wt,%Si)have been investigated by a new type of continu- ous directional solidification(CDS)apparatus.It's shown that the long casting with shining surface,homogeneous composition and structure can be produced within the adoptable ranges of process,and short-fine fibrous in situ composites of Al-Si eutectic and hyper-eutectic alloys can be made in some range of freezing rate depending on the silicon content by CDS technology.The flake/fibre transition of the eutectic silicon appears with increasing freezing rates from 0.02mm/s to 2.0mm/s,The tensile strength and percentage elongation increase with the increase of freezing rate.Compared with cast state Al-Si eutectic alloys,the strength of conti- nuously directionally solidified Al-Si eutectic alloys increases by 60%, its percentage elongation increases by two times,from 4% to 12%.The formation mechanism of the fibre structure and the effect of cutectic sili- con morphology on the cracking mechanism of Al-Si in situ composites have been analysed.