低Zn、高RE含量Mg－Zn－Zr－RE合金的相组成

PHASE CONSTITUTIONS OF Mg-Zn-Zr-RE ALLOYS WITHLOW Zn AND HIGH RE ADDITIONS

研究了低Ｚｎ、高ＲＥ含量Ｍｇ－Ｚｎ－Ｚｒ－ＲＥ合金的铸态相组成。在含高品位Ｙ的合金中，稀土相由晶界片状Ｘ相和晶内弥散分布的方形Ｍｇ＿（２４）Ｙ＿５相组成，并确定晶界片状Ｘ相为１８Ｒ调制结构，调制周期为０．２６ｎｍ。在含混合稀土的合金中，稀土相由Ｍｇ＿（１２）ＲＥ和晶内弥散分布的Ｍｇ＿（２４）Ｙ＿５相组成。分析表明，与ＭＢ２５合金相比，晶粒细化、稀土相的晶界强化和弥散强化可能是低Ｚｎ、高ＲＥ含量Ｍｇ－Ｚｎ－Ｚｒ－ＲＥ合金的强化原因。

The phase constitutions of Mg-Zn-Zr-RE alloys with low Zn and high RE addi-tions have been studied.In the alloys containing high purity-Y, the X phase at the grain bounda-ries(GBs) and the small square shaped Mg_(24)Y_5 phase in the grain interior are presented.The structure of the X phase is determined as the 1 8 R modulated structure with periodicity of 0.26nm. In the alloys containing Y-or Ce-rich mischmetals,the net-shaped Mg_(12)RE phase at the GBs and the small square-shaped Mg_(24)Y_5 phase in the grain interior are presented. As compared with the MB25 alloy, the grain refining and the strengthening by the rare earth com-pounds at the GBs and in the grain interior may cause the high strength of this kind of alloy.