摘要
采用钢模铸造法制备了不同含量的稀土元素铒的Al 6Zn 2Mg合金,利用金相组织观察、扫描电镜、透射电镜与能谱分析等分析测试手段,研究了铒在合金中的存在形式与细化机理。结果表明:铒在合金中主要有3种存在形式,即固溶到基体α(Al)中、形成初生Al3Er相或以共晶化合物的形式分布在晶界、以细小Al3Er形式在晶内析出;不同含量的铒能不同程度地细化晶粒,当铒含量不超过0.25%时,枝晶间距减少,但晶粒没有明显细化,当铒含量达0.4%时,细化效果已非常显著,随着铒含量的增大,晶粒略为细小;不同含量的铒对合金的细化机理取决于它在合金中的存在形式,当铒含量较低时,其细化机理符合传统的稀土铝合金细化机理,当铒含量较高时,由于在熔体中形成了初生Al3Er相,这些Al3Er相可以作为非均质核心而使晶粒得到细化,是合金的主要细化机理。
Al-6Zn-2Mg alloys containing different contents of Er were prepared by steel mould casting. The form of Er in Al-6Zn-2Mg alloy and its refinement mechanism were studied with OM, SEM, TEM and EDS. The results show that Er exists in three forms: resolved in α(Al based solid solution, forming primary phase Al_3Er or eutectic compound in grain boundary, precipitated in the form of the fine Al_3Er particles. The addition of Er can be capable of refining grain to a certain degree: the dendritical arm space of the alloy containing less than 0.25% Er becomes small, however the grain seldom keeps the same size. The effect of grain refinement becomes remarkably great when containing up to 0.4% Er. The grain becomes rather fine when the content of Er is more than 0.4%. The refinement mechanism of Er addition depends on the content of Er. The refinement mechanism of the alloy containing less Er conforms to the traditional theory for rare-earth aluminum alloy. The grain of the alloy containing more Er is refined because of the formation of primary Al_3Er, and the primary Al_3Er can act as heterogeneous nucleus.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2004年第4期620-626,共7页
The Chinese Journal of Nonferrous Metals
基金
国家重点基础研究发展规划资助项目(G1999064907)
