Effect Of Rare-earth Elements On Dynamic Recrystallization And Texture Of Az31 Wrought Magnesium Alloy During Hot-rolled

Magnesium alloy is the lightest structure materials, and has been extensively used in transport vehicles and 3C products, because of its low density, high specific strength, high thermal and electrical conductivity and easy recycling. Improving the mechanical properties of magnesium alloy has been an important subject in the research and development of magnesium alloy. A (0002)< 1120> basal slip usually develops preferentially during Mg alloys deformation, and for the rolled, Mg alloy sheets, the (0002) basal plane is strongly distributed parallel to the RD-TD plane, where the RD and TD are the rolling and transverse directions. In such a case, it is very difficult for the textured sheets to be deformed in the thickness direction, resulting in a poor formability.The experimental material in the present work is a hot-rolled AZ31 wrought magnesium alloy. The microstructures and texture of the rolled AZ31 alloys containing different contents of the rare-earth elements(Y,Ce) were investigated. The main conclusions are drawn as follows:Ce refines the microstructure of AZ31 wrought magnesium alloy. Moreover, the needle-like Al4Ce and the blocky Al10Ce2Mn7 particles were precipitated at grain boundary regions. The fine dot-like Al2Y particles phase was precipitated in grains by adding Y.The twin deformation in 1 st pass rolled Ce-containing alloy is much less than that of AZ31 alloy due to the non-basal slips were activated by Ce addition. However, there is no reduction of twin deformation in Y-containing alloy.There are two kinds of twin morphologies in AZ31, Ce-containing and Y-containing alloys. In AZ31 alloy, most of twins are contraction twins. However, most of twins in Ce-containing and Y-containing alloys are extension twins. The amount of extension twin increases with the increasing rare-earth elements content.The twin DRX is suppressed in rare earth-containing alloys. The DRX was accelerated by adding rare earth elements into AZ31 alloy.The (0002) plane texture which is distributed in RD-TD plane were formed in AZ31, AZ31-1.0wt%Ce and AZ31-1.3wt%Y alloy sheets. However, the intensity of (0002) plane texture in AZ31-1.0wt%Ce, AZ31-1.3wt%Y alloy was lower than that of the AZ31 alloy at the center parts. The basal texture was weakened significantly by adding rare-earth elements.The (0002) basal texture of AZ31 alloy was weakened by adding rare-earth elements (Ce,Y), for two reasons addressed below.①The non-basal slips were activated by rare-earth elements (Ce,Y) addition;②Rare-earth containing particles formed by adding rare-earth elements (Ce,Y) can increase the driving force for recrystallization and act as nucleation sites by generating local inhomogeneties in the strain energy and orientation. This can lead to PSN which provides more randomly oriented nuclei and results in weaker recrystallization textures.The addition of Y did result in a decrease of c/a ratio. It is considered the activation of non-basal slip system does stem from the change of crystal structure. On the other hand, the c/a ratio was slightly increased by addition of 1wt% Ce. Thus the change of crystal structure is not a direct reason for the activation of non-basal slip in the case of Ce addition.The results of EBSD measurement showed that besides (0002) basal texture, there was apparent peak intensity between (0002) and (1010) in AZ31-1.0wt%Ce and AZ31-1.3wt%Y alloy, suggesting the activation of non-basal slip system in RE added alloys.