(北京工业大学 材料科学与工程学院， 北京 100022)
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。
关键字: 铒; Al-Zn-Mg合金; Al3Er
element Er in Al-Zn-Mg alloy
（College of Materials Science and Engineering,
Beijing University of Technology, Beijing 100022, China）
Abstract: 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 Al3Er or eutectic compound in grain boundary, precipitated in the form of the fine Al3Er 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 Al3Er, and the primary Al3Er can act as heterogeneous nucleus.
Key words: Er; Al-Zn-Mg alloy; Al3Er
