Microstructure And Mechanical Properties Of Rapid Degradation Mg-3Zn-1Y-xCu(x=0,1,3,5) Alloys

On the basis of Mg-3Zn-1Y high-strength magnesium alloy,magnesium alloy material with rapid degradation behavior was developped by adding different content of Cu to meet the performance requirements of oilfield hierarchical fracturing ball and packer used materials during petroleum drilling engineering.The effect of the different Cu content on microstructure,mechanical properties corrosion properties in Mg-3Zn-1Y alloy is studied through the crafts of semicontinuous casting molding,hot extrusion,hot rolling,aging treatment,and the means of metallographic microscope,XRD phase analysis,SEM analysis,TEM analysis and mechanical properties tests and so on.?1?Deformed Mg-3Zn-1Y alloy is mainly composed of ?-Mg matrix,Mg₃Zn₃Y₂ phase and Mg3Zn6 Y phase,adding Cu inhibits the formation of Mg₃Zn₃Y₂ phase and reduces the number of Mg3Zn6 Y phase,while MgZnCu phase precipitates out a lot.Mg-3Zn-1Y-xCu?x=1,3,5?alloys are mainly composed of ?-Mg matrix,Mg3Zn6 Y phase and MgZnCu phase.?2?During the process of hot extrusion and hot rolling,dynamic recrystallization was took place in the Mg-3Zn-1Y-xCu alloys and the grain is refined.During the process of aging treatment,static recrystallization was occurred in the Mg-3Zn-1Y-xCu alloys,for extruded alloy,the static recrystallization grain is formed by MgZnCu particle stimulate nucleation;for hot rolled alloy,besides Mg ZnCu particles stimulate nucleation,the static recrystallization grain is nucleated by the induction of mechanical twins.?3?After the aging treatment,extruded Mg-3Zn-1Y-3Cu alloy shows better comprehensive mechanical properties,the ultimate tensile strength?UTS?,tensile yield strength?TYS?,elongation are 333 MPa,283 MPa,15.2%,respectively.Its ultimate compressive strength?UCS?,compressive yield strength?CYS?,compression ratio are 506 MPa,189 MPa,12.9%,respectively.Adding Cu changed the corrosion potential and corrosion current density of alloys.corrosion current density of Mg-3Zn-1Y-3Cu alloy reach largest value of 8.962A·cm^-2,it show that rapid degradation performance of Mg-3Zn-1Y-3Cu alloy is better,degradation rate is 0.41mm/day.?4?After the aging treatment,the ultimate tensile strength?UTS?,tensile yield strength?TYS?,elongation of hot rolled Mg-3Zn-1Y-3Cu are 352 MPa,292 MPa,13.1%,respectively.Compressive strength?UCS?,compressive yield strength?CYS?,compression ratio of hot rolled Mg-3Zn-1Y-3Cu are 465 MPa,364 MPa,8.5%,respectively.The improvement of the performance of the alloy mainly attributed to the formation of large deformation twin and grain boundary strengthening that the dislocation motion was obstacled by quasi crystal Mg3Zn6 Y phase and high melting point MgZnCu phase together.Corrosion type of hot rolled alloys is mainly pitting corrosion.With the increase of Cu content,rapid degradation performance of hot-rolled Mg-3Zn-1Y-xCu alloys is getting better and better,among the rest,degradation rate of Mg-3Zn-1Y-3Cu alloy is0.31mm/day.