Effect Of Heat Treatment And Surface Ultrasonic Rolling On The Corrosion Properties Of Mg-Y-Nd-Gd-Zr Allo

Compared with traditional Mg alloys,Mg-Y-Nd-Gd-Zr alloys have better mechanical properties at room temperature and high temperature,and their heat resistance is better than that of ordinary Mg alloys,which are widely used in aerospace and military fields.However,the low corrosion resistance of Mg-Y-Nd-Gd-Zr alloy limits its application in the shipbuilding industry.In order to further improve the corrosion resistance of Mg-Y-Nd-Gd-Zr alloy and expand its application range,it is an effective way to carry out appropriate heat treatment and surface nano-gradient strengthening treatment on the alloy.Therefore,in this paper,the effects of solid solution,solid solution aging treatment and surface ultrasonic rolling treatment on the corrosion resistance of Mg-Y-Nd-Gd-Zr alloy were analyzed,and the relationship between microstructure evolution and corrosion behavior was discussed in detail.The main results are as follows:The average grain size of the rolled state is about 41.52μm,and there are coarse Zr-rich particles.After 525C×8h solution treatment,the grain size grows to about120.72μm,and the Zr-rich second phase particles are dissolved in the magnesium matrix,but a large number of Y and Zr-rich second phase particles appear at the same time.After aging at 250°C for 36 h,the grain size is about 130.21μm,and the number of Y and Zr-rich second phase particles increases.The self-corrosion potential of the solid solution Mg-Y-Nd-Gd-Zr alloy increased from-1.70 V to-1.51 V,the self-corrosion current density decreased from 3.28×10^-3A/cm² to 2.50×10^-5A/cm²,and the Rct value increased from 81.21Ωto 837.92Ω.After aging treatment,the corrosion resistance of magnesium alloy decreases due to the precipitation of second phase particles.After USRP treatment,the grain size of Mg-Y-Nd-Gd-Zr alloy shows obvious gradient change.The microstructure of U-3 sample was characterized,and the grain size of the surface layer was refined to 187.14 nm.At this time,the gradient structure of magnesium alloy was composed of the surface SPD layer,the subsurface layer of the high density twin zone and the transition layer with slight deformation of the central matrix.U-3 sample has the best corrosion resistance.The corrosion potential increases from-1.70 V to-1.56 V,the corrosion current density decreases from 3.28×10^-3 A/cm²to 2.61×10^-5 A/cm²,and the charge transfer resistance is 1197.40Ωcm².The excellent corrosion resistance of magnesium alloy is determined by surface roughness,residual compressive stress,nanocrystals and the dissolution of second phase particles...