| Magnesium alloy is currently the lightest applied metal structural material.Because of its low density, high specific strength, good vibration damping capacity,easy recovery and many other advantages, it has widely used in the aerospace,automotive and other industries. However, due to the magnesium alloy is close-packedhexagonal structure (HCP) metals, it has less independent slip systems under roomtemperature, with low plastic deformation capacity and processing strain which greatlylimited the application of magnesium alloy. In this paper, dynamic plastic deformation(DPD) was subjected to hot-rolled and annealed commercial AZ31sheet with strongbasal texture. And the texture evolution and mechanical properties of AZ31magnesiumalloy after DPD were observed and analyzed using metallographic observations (OM),electron backscatter diffraction technique (EBSD), X-ray diffraction (XRD) andmechanical properties testing. The main conclusions are as follows:①The DPD whose loading direction is along the rolling direction (RD) makesAZ31samples generated lots of {10-12} tensile twin. The twin volume fraction firstincreases and then decreases with the increasing of DPD strain with the strain of theinflection point is near5%. Meanwhile, the orientation of grains in samples changesgreatly during DPD. The basal texture gradually weakened, and the twinning texturegradually enhanced. The spacing of {10-12} twin lamellar decreases with the increasingof DPD strain.②Samples after DPD occur the detwinning when tensiled along the RD direction(referred to the0°tension). And the twin volume fraction of different samples withdifferent DPD strains decrease greatly from13%,35%and66%, respectively, reducedto3%,2%and9%. Also the texture of AZ31samples change greatly after0°tension.The initial basal texture is recovered and the twin texture generated by DPD isweakened; But no such changes are found in the samples which are tensiled along theND direction(referred to the90°tension). When samples are subjected to this kind oftension the twin volume fraction and the orientation of mostly grains keep the same.③The yield strength of the AZ31samples after DPD reduces sharply due to theoccurrence of detwinning during0°tension. And the {10-12} twin induced by DPDdisappears during this tension; When90°tension is conducted to AZ31magnesiumalloy after DPD deformation, the yield strength of the materials have constant increases with the increases of DPD strain which may be due to the hindering the dislocation slipby the twin boundaries; But both the0°and90°tension samples after DPD deformation,the tensile strength of the materials almost have no change, showed DPD has a smallereffect on the tensile strength.In order to analysis the only effects of detwinning and {10-12} twin lamellarstructure on the mechanical properties of magnesium alloy, the samples are annealed toremove the dislocations induced by DPD and the stress concentration.④The yield and tensile strength of the materials are found increasing with theincreasing of DPD strain during0°tensile of the AZ31alloys with different DPD strainsafter annealing for stress relieving, and the tensile strength even reaches as high as274Mpa. And its increasing ratio is more apparent than that of non-annealed samples,which is because of the change of texture making the orientation changed to difficult todeform, and we refer this to the enhancement of texture; While the yield and tensilestrength of the materials are found almost no change compared to the materials beforeDPD during90°tensile. Since during this tension the AZ31magnesium alloy have nodeformation of twinning and no enhancement of twin. The "refinement" of grainsinduced by the dividing of {10-12} twin layer has little effect on their mechanicalproperties. These show that the twin strengthen has more effective on the mechanicalproperties of AZ31alloys compared to the strengthening of twin boundaries. |
PDF Full Text Request