复合添加Y和Nd对Mg-Li合金显微组织及室温压缩织构的影响

采用OM,SEM,XRD,EBSD及电子万能试验机,对比研究了Mg-5Li-3Al-2Zn和Mg-5Li-3Al-2Zn-1.2Y-0.8Nd铸态合金的显微组织、力学性能以及室温单向压缩后的织构演变.研究发现,复合添加Y和Nd 2种稀土元素后,合金中絮丝状AlLi相明显减少,晶粒得到显著细化,平均尺寸在30μm左右.2种合金的塑性表现良好,加入少量稀土的合金室温压缩的变形量可达到27%.复合添加的稀士元素大幅度降低了Mg品格的c/a值,显著弱化了合金的基面织构,激活了锥面滑移系的同时,也使得室温下少见的柱面滑移破激活.

EFFECTS OF COMBINED ADDITION OF Y AND Nd ON MICROSTRUCTURE AND TEXTURE AFTER COMPRESSION OF Mg-Li ALLOY AT ROOM TEMPERATURE

Due to the super light-weight property,Mg-Li alloys are very promising in the fields of aerospace and military defense.Up to now,many studies about hot deformation behavior of Mg-Li alloys have been reported.However,there are little researches on their room-temperature deformation behavior.Therefore,the plastic deformation mechanism of Mg-Li alloys needs further investigated.It is known that addition of RE to Mg alloys could cause solid solution strengthening, fine grain strengthening and secondary phase strengthening.Nevertheless,reports refer to the effect of RE on the texture of Mg-Li alloys.This work was devoted to study the microstructure,mechanical properties and the evolution of texture after compression at room-temperature of the as-cast Mg-5Li-3Al-2Zn and Mg-5Li-3Al-2Zn-1.2Y-0.8Nd alloys with OM,SEM,XRD,ODF and EBSD techniques as well as material testing machine.The results show that with the addition of Y and Nd,most of the filamentous AlLi intermetallic compounds are suppressed and substituted by other two intermetallics Al₂Y and Al₁₁Nd₃.Meanwhile,the grains are refined with the average size of 30μm.ODF analysis indicates that for Mg-5Li-3Al-2Zn alloy,when the strain is 0.17 the C-axis of most grains is roughly 75°form ND,while in Mg-5Li-3Al-2Zn-1.2Y-0.8Nd,when the strain is 0.10 the strong prismatic texture appeares,which means that the（1010） of most grains parallel to ND. Both of the two alloys exhibit high plasticity when tested at room-temperature,while the compression deformation of the alloy containing Y and Nd can reach up to 27%.The combined addition of Y and Nd significantly reduces the c/a of the magnesium lattice,weakes basal texture,activates the pyramidal slip system and,especially,activates the prismatic slip system which seldom occurs at room-temperature in magnesium alloys.