Study On Strengthening And Toughening Mechanism And Hot Deformation Behavior Of Mg-Li-Al-Y Alloy

In this paper,Mg-Li alloy is used as the research object.By adding a trace amount of aluminum and rare earth yttrium,the Mg-Li alloy is guaranteed to be plastic while improving its strength.The microstructure evolution during tensile fracture and thermal deformation behavior of Mg-4 wt.%Li-1 wt.%Al-0.5 wt.%Y alloy were systematically studied,and the mechanism of strengthening and toughening as well as the law of microstructure evolution during thermal deformation were revealed.Firstly,the dense and defect-free Mg-4Li-1Al-0.5Y alloy was successfully prepared by casting process.Phase analysis shows that the annealed alloy was mainly composed of the ?-Mg phase and the Al₂Y phase,with an average grain size of 10.15 m.Moreover,the axial ratio c/a value of the alloy was 1.605 by TEM and XRD analysis.EBSD observations of the microstructure revealed that there were weak <11???0> prismatic texture and basal texture in the annealed alloy.Through the in-situ tensile EBSD analysis of its toughening mechanism,it was found that the alloy showed strong characteristics of work hardening,and the basal slip and non-basal slip played a dominant role in the whole process of tensile deformation,while twins played a coordinating and complementary role.When the high temperature compression behavior of the alloy was studied,it was found that the alloy also exhibited the characteristics of work hardening.By analyzing the thermal deformation mechanism,it is found that the reduction of the axial ratio c/a makes the non-basal slip more easily activated,the dislocation density is larger and the cross slip occurs,which further suppresses the activity of the twins.As a result,the slip is always dominant and the compression curve shows work-hardening.Further research on its high-temperature tensile deformation process revealed that the alloy exhibited typical dynamic recrystallization softening curve characteristics.As the temperature increased,more pronounced steady-state rheological characteristics appeared in the later stage of deformation.Microstructure observation shows that the main deformation mechanism is slip at low temperature,while dynamic recrystallization is the main deformation mechanism at high temperature.