Study On Deformation Mechanism Of Rare Earth Magnesium Alloy Containing LPSO Phase Under Different Stress Conditions

High-strength and heat-resistant rare earth magnesium alloys have a broad application space in aerospace due to their light weight and excellent room and high temperature performance.The Mg-Gd-Y-Zn-Zr alloy contains a unique long period stacking ordered(LPSO)phase,which,as a new type of reinforcement phase,can further improve its performance and has gained wide attention.In order to achieve the overall forming of components under complex stress states,it is particularly important to study the differences in microstructures and deformation mechanisms under simple stress states.In this paper,the Mg-13Gd-4Y-2Zn-0.5Zr alloy is used as the research object,and the Gleeble thermal simulator is used to conduct torsion and compression experiments to achieve shear stress and compressive stress deformation.We analyze the changes of alloy deformation behavior and deformation mechanism under different deformation conditions,and provide a basis for the study of the complex stress state of rotary extrusion.The conclusions are as follows:The rheological curves of the alloy deformed by shearing and compressive stress show dynamic recrystallization characteristics.The shear stress deformation peak stress is slightly larger than the compressive stress deformed alloy,but the critical dynamic recrystallization stress and critical dynamic recrystallization strain are both smaller than the compressive stress deformation,and dynamic recrystallization is easier to stimulate.In the process of deformation,both shear and compressive stress deformed alloys have gradient structures.Decrease the deformation temperature and increase the deformation rate,the degree of kinking of the LPSO phase increases while the dynamic recrystallization fraction decreases.There are obvious differences in the microstructure with different strain positions in shear and compression stress.At the critical dynamic recrystallization strain position,the kink angle of the compressive stress-deformed alloy is larger.The shear stress alloy grains at the position of maximum strain are only slightly deformed,the compressive stress alloy grains are significantly compressed along the ED direction and become streamlined,and the LPSO phases of different forms are violently kinked.The activation sequence of the deformation mechanism of alloys in different stress states is slip,kink,and twinning.The internal dislocation density of shear stress deformed alloy is lower than that of compressive stress.Under different deformation conditions,the schmid factor of the basal and non-basal slip systems of the shear stress deformed alloy is almost higher than0.3,which means that the non-base surface slip is easy to start.The schmid factors of cylinder slip and pyramidal <a> slip of the compressive stress deformation alloy are low,including the non-basal slip system is difficult to start.Due to the active slip,the shear stress deformed alloy has a small kink angle under the same deformation conditions.The kink band has parallel and beak shapes,and only a small amount of tensile twins appear,showing parallel or cross-like distribution.There are a large number of kink bands in compressive-stress alloy,almost all of which are parallel distribution perpendicular to the compression direction.Tensile twins and compressive twins appear at the same time,and the number of twins increases,mainly in parallel distribution,which contributes more to deformation.The hardness of deformed alloys in different stress states are improved,and the hardness increases with the decrease of temperature and the increase of strain rate.The properties of compressive stress-deformed alloys have obvious anisotropy,with obvious differences in different regions.The shear stress deformed alloy has more uniform mechanical properties,and the edge hardness is high,which is easier to meet the actual engineering needs.