Research On Anisotropic Behavior Of A Mg-Gd-Y-Nd-Zr Alloy Extruded Plate

Magnesium alloys have broad application prospects in aerospace due to their advantages of low density,high specific strength and specific stiffness.However,mechanical behavior anisotropy limits the application of magnesium alloy deformation parts.Up to now,researchers have carried out a wide range of research on the anisotropic behavior of magnesium alloy plate in the ND-plane,which provided important guidance for the engineering application of magnesium alloy.However,there is still a lack of in-depth research on the anisotropic behavior in the cross section of a plate.Nevertheless,in some special plate-shaped parts,there is also high requirement for mechanical properties of the cross-section of the plate.Therefore,it is necessary to study the anisotropic behavior of magnesium alloy in the cross-section.Based on the preparation of an Mg-8Gd-4Y-Nd-Zr alloy extruded plate,the mechanical behavior anisotropy of compression and tension in the cross section of the plate with different ageing states was studied.The conclusions are listed as follows:(1)The compression properties of the cross section are studied and the formation mechanism of anisotropy is revealed.When the sampling direction is 90° to the normal direction of the plate and the aging state is peak-aged state,the performance is the best,the compressive strength is 571 MPa and the compression strain is 14.2%;When the angle between the sampling direction and the normal direction of the plate changes from 0° to 90°,the compressive strength and compression strain of the alloy decrease first and then increase with the increase of the angle.When the alloy is compressed in the direction of 45°,both the compressive strength and the compression strain are the lowest.In the 45° sampling direction,the main deformation mechanism is basal slip and tension twinning;In other directions,the main deformation mechanism is the basal slip and prismatic slip,and the compression twinning and tension twinning coordinate together;In addition,the larger average grain size and the higher volume fraction of coarse second phase particles in the 45° direction are also the reasons for the poor performance in this direction.(2)The failure mechanism of the compression fracture is proved.During the deformation process,the alloy shows the fracture characteristics of ductile brittle mixture,but the samples with different sampling angles and aging states are different.From the sampling point of view,under the same aging state,the number of cleavage surfaces in the 45° direction of the alloy is more than that in other directions.From the point of view of aging state,in the case of a certain sampling direction,in the solid-solution state,the fracture has the most dimples and the least cleavage surfaces,which shows the mixed fracture mechanism of toughness and brittleness dominated by ductile fracture.In the peak-aged state,the number of cleavage surfaces is the most and the number of dimples is the least,which shows the mixed fracture mechanism of toughness and brittleness dominated by brittle fracture.(3)The anisotropic characteristics of tensile properties on the cross-section and the formation mechanism are proved.The rule of mechanical properties versus sampling direction of solid-solution state and over-aged state samples are similar.The mechanical properties of the samples loaded at 90° are better.The rule of mechanical properties versus sampling direction of under-aged and peak-aged samples are similar,and the mechanical properties are relatively better when the loading direction is 0 ° and 22.5 °.The reasons can be summarized as follows:(1)In the under-age state and peak-aged conditions,the grains are "hard",the intergranular coordination deformation ability is weakened,leading to premature fracture and poor performance;(2)The difference of the number of second phase particles in different sampling directions leads to the anisotropy of tensile properties.(4)The tensile fracture failure mechanism of the sample is proved.The fracture surface of all the tensile samples show the characteristics of delamination,and a lot of coarse second phase particles can be observed in the fracture;From the point of view of aging state,when the sampling direction is the same,the number of dimples and the cleavage surface of solid-solution state samples are the most and the cleavage surface is the least.There are a large number of cleavage surfaces and a small number of dimples in the under-aged and peak-aged states.In the over-aged state,the main fracture is intergranular fracture.From the perspective of sampling direction,under the same aging state,the number of cleavage surface and coarse second phase particles is the largest in the 45° direction or near 45° direction.