| Research on medical implanted metal materials is undergoing a transition from permanent to absorbable metallic materials.Zinc and its alloys have become a new type of biodegradable biomaterial with great research value and development prospects due to its good biocompatibility and suitable degradation rate.However,because of the relatively poor mechanical properties of zinc,studying how to improve the mechanical properties of zinc while ensuring its suitable degradation rate becomes the real clinical application of zinc alloy.In this paper,Zn-Mg-Al alloys with different compositions were designed and prepared,and the Zn-Mg-Al alloy was hot-rolled at 200? to improve its mechanical properties.The microstructure,mechanical properties and degradation properties of the alloy were evaluated by SEM,XRD,hardness,tensile,electrochemical and weight loss rates.The as-cast Zn-1Mg alloy is mainly composed of dendrites ?-Zn,Mg2Zn11 and Zn eutectic phases at the grain boundaries,and a trace amount of non-equilibrium MgZn2 phase.With the addition of aluminum,the black eutectic structure and the nonequilibrium phase Mg2Al3 appear in the alloy,and as the Al content increases,the dendrite volume gradually decreases,and the Zn and Al eutectic structure gradually increases and the grains within the alloy are smaller.After the homogenization treatment,the non-equilibrium phase of the alloy disappear,the eutectic structure changes,and the composition is more uniform.The hot rolling treatment causes the alloy structure to be broken and refined,and the dendrites and the second phase are fractured and deformed in the rolling direction,exhibiting characteristics of the deformed structure.At the same time,the alloy structure is also finer.The hardness of as-cast Zn-1Mg-xAl(x=3,4,5)alloy decreases with homogenization;after hot rolling deformation,the hard and brittle phases in the alloy are broken and evenly distributed along the rolling direction,thereby increasing the hardness of the alloy,and the hardness of the alloy is up to 105HV1.As the amount of aluminum in the Zn-Mg-Al alloy increases,the distribution of the hard second phase in the alloy is more uniform,which also leads to an increase in the hardness of the alloy.The tensile results show that the tensile strength of as-cast Zn-1 Mg-xAl(x=0,3,4,5)alloys is 155MPa,204MPa,232MPa and 250MPa,respectively.And the elongation of all four alloys is less than 1%.After hot rolling deformation,the tensile strength of the alloy is 264MPa,329MPa,338MPa and 359MPa,respectively,and the yield strengths are 200MPa,222MPa,281 MPa and 309MPa,respectively,and the elongations are 5.1%,8.0%,12.2%and 5.2%,respectively.Electrochemical test results show that the electrochemical corrosion patterns of the four alloys are basically the same.The as-rolled Zn-Mg alloy has a self-corrosion potential of-1.135V,a self-corrosion current density of 7.97?A/mm2,and a polarization resistance of 215.6?.Compared with the as-rolled Zn-Mg-Al alloy,its self-corrosion potential is more positive,self-corrosion current density is smaller,and polarization resistance is larger.The self-corrosion current densities of as-cast and hotrolled Zn-1Mg-5Al alloys are 13.6?A/mm2 and 10.06?A/mm2,respectively.Compared with hot-rolled zinc alloys,the as-cast zinc alloys have higher electrochemical corrosion rates.The addition of the alloying element A1 causes the corrosion resistance of the alloy to decrease,while the hot rolling causes the electrochemical corrosion tendency of the alloy to be weakened.The weight loss test results show that the corrosion rate of each component alloy fluctuates in the early stage of immersion,and the final corrosion rate decreases and tends to be stable.The corrosion rates of the as-cast Zn-1Mg-xAl(x=0,3,4,5)alloy are 0.117mm/a,0.124mm/a,0.134mm/a and 0.145mm/a,respectively.The corrosion rate of the corresponding rolled alloy is 0.099mm/a,0.124mm/a,0.130mm/a and 0.150 mm/a,respectively.The degradation rates of the four alloys from low to high are:Zn1Mg,Zn-1Mg-3Al,Zn-1Mg-4Al,Zn-1Mg-5Al. |
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