Study On Mechanical Properties And Corrosion Of Biodegradable Zn-Cu Alloy

Biodegradable metal have attracted much attention due to their excellent mechanical properties and degradability.Researchers foCus on magnesium-based alloys and iron-based alloys in the past several decades,however,their excessive or too slow corrosion rate hindered the clinical use process.At present,the study of biodegradable zinc alloy is still at the initial stage,only limited literatures have reported.In this study,Cu was added into zinc in order to improve its mechanical properties,and the effects of Cu content on the mechanical properties and corrosion properties of Zn-Cu alloys were investigated.Then,heat treatment and equal channel extrusion were conducted on the alloy to improve it mechanical properties.Considering the corrosion behavior of the material,The corrosion behavior of the materials in simulated body fluid was determined by immersion tests and potentiodynamic measurement.The addition of Cu element can improve the strength of the alloy.With the increase of the element content,solid solution strengthening and second phase strengthening would increase the strength and hardness of Zn-Cu alloy.The elongation of the alloy increases at the beginning and then decreases with the increase of Cu content,it reaches a maximum when the content of Cu is 1 wt%.Zn-Cu alloy was extruded by equal channel angular pressing(ECAP)at 230?with different passes.Experimental results showed that the grains were broken by ECAP,and after ECAP some shear bands and refined grains appeared in micro structure.It was observed that the mechanical properties(mainly strength and ductility)were improved after ECAP processing.the strength and elongation of Zn-2.5Cu increased from 120MPa,0.5%to220 MPa,35%after the ECAP 2 passes.After ECAP 3 passes,the plasticity of sample is improved and the strength decreases.The tensile fracture surface of the specimens have obvious dimple features.The heat treatment has a significant effect on the microstructure of the alloy.The grain boundary is more clear and the grain is finer after heat treatment at 300? for 1 h.The results showed that heat treatment before alloy ECAP 3 pass can relieves internal stresses,and then,benefit the plastic deformation.The sample ECAP 3 pass after heat treatment at 300? showed smaller grain size and higher strength and elongation.The strength and elongation are 180 MPa and 45%,respectively.The corrosion behavior of the materials in simulated body fluid was determined by electrochemical test and immersion tests.The electrochemical test result showed that Zn and its alloys have a high self-corrosion potential and low corrosion rate.the corrosion rate increases with the increase of Cu content but the effect is small,the degradation rate of Zn-2.5Cu is only 0.045mm/year,significant lower than the corrosion rate of magnesium alloy.After ECAP process,the corrosion rate of Zn-Cu alloy increase,and faster than Fe-based alloy.Thro ugh immersion test,we can see Zn-Cu alloy presents uniform corrosion morphology in SBF.The EDS results showed that the corrosion products mainly contain P,Ca,C,and O,according to the literature,corrosion products may contain phosphate and carbonate.These results indicate that Zn-Cu alloys has the potential to be a new biodegradable metal.