The Effect Of Mn,Sr And Sn On Glass Forming Ability,Corrosion And Compressive Properties Of Mg-Zn-Ca Alloy

Comparing with other implant materials,magnesium and its alloys exhibit unparalleled advantages in the density,strength and elastic modulus.In recent years,the development of suitable magnesium alloys as metallic implant material has attracted increasing attention.However,the application of magnesium and magnesium alloys is limited mainly due to their poor corrosion resistance.The reported investigations suggest that Mg-Zn-Ca series amorphous alloys,which possess good biocompatibility,excellent mechanical properties and corrosion resistance,could meet the clinical requirements,and they have potential applications as biodegradable medical materials.However,research on the glass forming ability and corrosion degradation behavior of Mg-Zn-Ca system is still relatively limited.In the present work,Mg₆₅Zn₃₀Ca₅ was selected as the base alloy.Ribbon and rod samples of Mg₆₅Zn₃₀Ca₅ doped with Mn,Sr and Sn elements were prepared by melt spinning and copper mold casting.The influence of Mn,Sr and Sn?biodegradable elements?on the amorphous forming ability,corrosion and compressive properties of Mg-Zn-Ca alloys were studied by XRD,SEM,DSC,electrochemistry tests and compression experiments.The obtained results are as follows:?1?The influence of Mn.The ribbon and rod samples of Mg₆₅Zn₃₀Ca₅ alloy are completely amorphous.With addition of different amount of Mn element,the ribbons samples of the Mn-free and Mn-doped alloys still remain amorphous structure.However,Mg,Mn and MgZn phases gradually precipitate in the 2mm rod samples with increasing addition of Mn.It is indicated that the addition of Mn element damages the amorphous forming ability of Mg₆₅Zn₃₀Ca₅ alloy.Electrochemical and immersion tests of 2mm rod samples show that the corrosion resistance of the amorphous state Mg₆₅Zn₃₀Ca₅ alloy is the best,adding 0.2at% of the Mn element has little effect on the corrosion resistance of the alloy,and further addition of the Mn element significantly decreases the corrosion resistance of the Mn-doped alloys.Compression test shows that the strength of Mg₆₅Zn₃₀Ca₅ is the highest?531.8MPa?,while the strength gradually decreased by adding Mn element.?2?The influence of Sr.The results show that the glass forming ability is first enhanced with increasing addition of Sr element.The alloy containing 1at% Sr exhibits the largest glass forming ability.Further addition of Sr element weakens the glass forming ability of Mg₆₅Zn₃₀Ca₅ alloy.The results of electrochemical and immersion experiments about 2mm and4 mm rods samples show that the corrosion resistance of the Sr-containing samples is better than that of the Mg₆₅Zn₃₀Ca₅ samples.In other words,the addition of Sr element enhances the corrosion resistance of the Mg₆₅Zn₃₀Ca₅ alloy alloy.The results of compressive mechanical properties test show that the compressive strength are improved by 4.07%,7.06% and 1.57%with addition of 0.5at%,1.0at%,1.5at% Sr element,correspondingly,while little change is observed for the plasticity of the alloys.?3?The influence of Sn.The ribbon samples with different content of Sn element are all in fully amorphous state.While the structure of the 2mm rod sample changes from complete amorphous state to the polycrystalline state composed of Mg phase and Mg2 Sn phase with increasing addition of Sn.The volume fraction and size of precipitated crystal phase increase with the increment of Sn content.It is indicated the doped Sn element decreases the glass forming ability of the Mg₆₅Zn₃₀Ca₅ alloy.The results of electrochemical test,immersion and compression experiment show that the corrosion resistance and compressive strength of Mg₆₅Zn₃₀Ca₅ alloy gradually decrease with the increasing addition of Sn element.