| In this paper,rolled-plate AZ31 magnesium was subjected to friction stir processing.The different grain sizes of fine-grain AZ31 magnesium alloy were prepared by friction stir processing with different processing parameters in air and tow-pass friction sir processing under water.The corrosion fatigue behavior of stir zone was studied in air and in 1% Na Cl solution.The mainly results are as follow:The different grain sizes of AZ31 magnesium alloy were prepared by friction stir processing with different processing parameters at room temperature.The average grain sizes were 1.2 ?m,3.5?m,8.5?m respectively in the stir zone.The grain size increases with the increase of the hot-input.Two-pass friction stir processing produce fine grain of 1.2 ?m.The texture type changes after FSP,which is beneficial to the basal slip.The basal texture under different processing parameters is same.The fatigue anisotropy are showed in different processing direction.The fatigue strength in TD is higher than in PD,the fatigue limit strength is 130 MPa?90 MPa respectively.The S-N curve equation of ultrafine grain size obtained in air in PD: lg N=2.3676-0.068lg?.The S-N curve equation of ultrafine grain size obtained in air in TD: lg N =2.2555-0.032lg?.The fatigue in 1% Na Cl solution is same as in air and TD is stronger than PD.The grain refinement can improve the corrosion fatigue strength by effect deformation behavior and reduce corrosion rate after 500 thousands cycles ago.Texture mainly affects the degree of deformation.The texture of FSPed AZ31 magnesium is favorable to slip in PD,and it can be found that there are many slip bands in the fracture zone,and the slip steps are dense and narrow.On the contrary,it is difficult to slip in TD and the slip steps are broad and low because of grain orientation.The twinning deformation and slip were initiated at the same time due to the grain size of base material is coarse and has the rolling texture.The fracture showed torsion slip bands. |
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