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 30 mu m. 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 degrees 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 < 10 (1) over bar0 > 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.