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富钇混合稀土对Mg-Zn-Zr系镁合金的铸造组织及组成相无显著影响。MB25合金(含高纯金属钇)和MB26合金(含富钇混合稀土)的铸造组织都是在α-Mg晶界上分布着大量的Z+β网状共晶化合物相(以Z相为主),其区别在于铸态MB26合金的晶界共晶相中溶有少量的镧、铈、错、钕、钆和镝等多种稀土元素。均匀化处理和挤压热加工都能使铸态MB26合金发生不同程度的相变,并在不同程度上改变铸态合金的组织和相结构。随着从挤压到均匀化处理温度的提高,其相变过程是从Z相中锌的扩散相变开始到β、W共晶相各自完成共析转变结束。
Yttrium-rich mischmetal had no significant effect on the microstructure and composition of Mg-Zn-Zr-based magnesium alloy. The castings of MB25 alloy (including high-purity metal yttrium) and MB26 alloy (including yttrium-rich rare earth) are all distributed in the α-Mg grain boundary with a large number of Z + β reticular eutectic phase ). The difference is that rare earth elements such as lanthanum, cerium, maltose, neodymium, gadolinium and dysprosium are dissolved in the grain boundary eutectic phase of the as-cast MB26 alloy. Homogenization and extrusion heat treatment can make the as-cast MB26 alloy undergo different degrees of phase transformation and change the microstructure and phase structure of the as-cast alloy to varying degrees. With the increase of temperature from extrusion to homogenization, the phase transformation process starts from the diffusion transformation of zinc in Z phase to β, and the eutectic phase completes the eutectoid transformation respectively.