Microstructure And Properties Of Degradable ZnMgMnGd Alloys

Zinc and its alloys are expected to become new generation of biodegradable metal materials because of excellent biocompatibility and moderate degradation rates.However,the mechanical properties of pure Zn are poor.To ensure the synergy of the mechanical properties and corrosive properties of Zn alloy,in this article,based on ZnMgMn alloy,the mechanical properties and corrosion resistance of zinc alloy are improved by adding different amounts of Gd and heat treatment.The tissue,mechanical properties,degradation properties and electrochemical properties of casting and heat treatment alloy are analyzed.The main results obtained are as follows:（1）The casting ZnMgMn alloy is mainly composed ofα-Zn phase,Mg₂Zn₁₁ phase,Mg Zn₂phase and Mn Zn₁₃phase.After adding the rare-earth Gd,the alloy produces a Gd Zn₁₂ phase.The heat treatment process can’t change the phase composition of the alloy.With the increasing content of Gd,the alloy communist crystal organization is changed from divorced common crystal to laminar shape.With the increase of the cooling speed,the grain size and the sheet spacing of crystal tissue decreases in the alloy.With the aging time,the Gd Zn₁₂ phase organization grows in the alloy.（2）With the increase of Gd elements content in the casting ZnMgMn alloy increased,the alloy microhardness firstly increased and then decreased.And the highest microhardness of the alloy with the addition of 0.6wt.%Gd is 217HV,which is 28%higher than the matrix alloy.With the increase of cooling speed,the microhardness of ZnMgMn Gd alloy is gradually improved.And the highest microhardness of water bath cooling alloy is about 265.3HV,which is 22%higher than the casting alloy.With the extension of the aging time,microhardness of the alloy is firstly increased and then reduced.And microhardness of the alloy that aged 4h is about 258.6HV,which is 19%higher than the casting alloy.（3）With the increase of Gd element content in the casting ZnMgMn alloy,the degradation rate of alloy firstly decreases and then increases.And the lowest degradation rate of alloy with the addition of 0.6wt.%Gd is about 0.259mm·a^-1,which is 54%lower than the matrix alloy.With the extension of the aging time,the degradation rate of ZnMgMn Gd alloy firstly decreases and then increases.And the lowest degradation rate of the alloy that aged 6h with oil bath is0.188mm·a^-1,which is 27%lower than the cast alloy.In the process of corrosion,the alloy are mainly included uniform corrosion and accompanied by local corrosion.The corrosion products of alloy mainly consist of zinc（magnesium）oxide,zinc（magnesium,calcium）phosphate and zinc（magnesium,calcium）carbonate and other substances.（4）With the increase of Gd elements content in the casting ZnMgMn alloy,the corrosion rate of alloy firstly decreases and then increases.And the lowest corrosion rate of the alloy with the addition of 0.6wt.%Gd is 0.3mm·a^-1,which is 62%lower than that of ZnMgMn alloy.With the increase of cooling speed and the extension of aging time,the corrosion speed of ZnMgMn Gd alloy decreases first and then increases.The lowest corrosion rate of alloy that aged6h with oil bath is 0.116mm·a^-1,which is 61%lower than the cast alloy.There are 37 figures,16 tables,and 86 references in this article.