稀土对Al-20Si-2Cu-1Ni铝合金组织和性能的影响

借助金相(OM)、扫描电镜(SEM)、能谱分析(EDS)等技术,研究了富Ce混合稀土(RE)对Al-20Si-2Cu-1Ni高硅铝合金共晶硅变质、稀土化合物及力学性能的影响,并探讨其机理。结果表明,RE能有效变质共晶硅,随RE添加量的增加,变质效果不断增强,同时针片状RE化合物也逐渐增多。RE通过在凝固前沿富集从而抑制共晶硅的生长,但是过量的RE将导致固溶Cu、Ni的针状化合物(Al_2Si_2RE)生成,抵消了共晶硅变质对合金性能改善的一部分作用,使合金力学性能反而有所下降。添加0.6%RE时,铸态高硅铝合金的抗拉强度和伸长率分别达到最大值,较变质前分别提高33%和230%。

Effects of RE on microstructures and properties of Al-20Si-2Cu-1Ni aluminum alloy

The effects of Ce-rich Rare Earth (RE) on modification of eutectic silicon, formation of RE compound, and mechanical properties of Al-20Si-2Cu-1Ni high silicon aluminum alloy have been studied by use of optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The mechanism was also discussed. The results show that, RE can modify eutectic silicon effectively which show better modification with increasing amounts of RE. While it also cause formation of needle-like RE compounds which increase with increasing amounts of RE. The mechanism of eutectic silicon modification is that the growth of eutectic silicon is hindered by the RE elements enriched at solidification front. But the excess RE will lead to form acicular Al2Si2RE compound containing a few solution of Cu and Ni elements which can offset part of the improvement of mechanical properties contributed by eutectic silicon modification. As a result, the mechanical performances of this alloy decrease with more acicular Al2Si2RE compound formation. With addition of 0.6% RE to the melt, the tensile strength and elongation of casted high silicon aluminum alloy reach maximum values which improve by 33% and 230% respectively, compared to the case without RE.