Investigation On HPT-processed Microstructure Evolution And Hot Deformation Behavior For Biomedical Magnesium Alloys

Magnesium alloys have significant advantage as d egradable biomaterials for its excellent biocompatibility and mechanical compatibility, and have already become an important aspect in the field of biomedical metallic materials. However, it is difficult to achieve precise plastic deformation because of th eir poor ductility. The main aim of experiment is to introduce the high pressure torsion method for improving the performance of magnesium alloy. The experiment results indicate that Mg-0.8Ca%-3%Nd alloy is made up of the α-Mg matrix phase, the secondary phases consist of Mg41Nd5 and Mg2 Ca. Moreover, there is no evidence for the formation of any new phases, just the slip plane transforms. This transformation is beneficial to plastic deformation of magnesium alloy due to an increase in the available slip plane. Similarly, the phase transformation does not occur,the slip plane of WE43 alloy has transformation from pyramidal slip to basal slip. The secondary phases along the grain boundaries of Mg-0.8Ca%-3%Nd alloy is broken and tends to a more uniform distribution with increasing the number of rotation, and the microhardness value increased significantly. Excellent grain refinement of WE43 alloy is achieved after HPT for 10 turns and its size is 200~300nm.Magnesium alloys can cause dynamic recrystallization much more easily because of the low stacking fault energy. Therefore, the DRX becomes one of effective approach to improve integrated performance of magnesium alloy. I n order to provide a necessary basis for the following EC AP processing of magnesium alloy, the hot compression test is conducted on the WE43 magnesium alloys, and combined with hot processing maps to study the flow behavior of magnesium alloy under different strain rate and deformation temperature. The experimental results indicate that the flow stress of this alloy decreases with increasing of deformation temperature and decreasing of strain rate. The flow stress fit with hyperbolic-sine modeling. According to the microstucture at different deformation condition and the hot processing maps of this alloy, the optimal processing zone is 400 ~ 450 ℃ /0.003 ~ 0.02s-1. In this processing region, the dissipated energy contributed to the evolution of microstructure is larger, and it benefits to dynamic recrystallization. The microstructure observation shows that some small as well as equiaxial dynamic recrystallization distributed uniformly inside overall alloy.