Study On Modification And Degradability Of Mg-2Zn-0.2Mn-xCa Biomedical Magnesium Alloy

As the level of medical technology has been developed greatly,the global population has been continuously growing and tends to the problem of aging,which results in a constant increase in the proportion of sudden fracture disease.The treatment of fractures usually requires a fixed support for the support scaffold,providing a relatively fixed tissue repair environment for bone tissues.Therefore,in recent years,the demand for bone repair stent material has been increased dramatically.Commonly used metal bone repair materials usually require secondary removal surgery,which adds more pains and extra medical expenses to the patients.With biodegradability and good mechanical compatibility,the magnesium alloy has a great potential as a degradable bone repair materials for the treatment of fracture disease.However,nowadays,due to the degradation rate of magnesium alloy and human bone tissue healing rate was significantly different,too fast degradation rate of magnesium alloy will lead to its early loss of mechanical properties,thereby affecting the healing of bone tissue.Thus,this paper attempts the new process to modify the Mg-2Zn-0.2Mn alloy by adding different Ca-containing and different heat treatment processes in order to control the degradation rate of the alloy to a certain extent,and finally,employing the cell compatibility test to evaluate the cell compatibility of heat treated modified magnesium alloy.Well-type resistance furnace has been firstly used to smelt three different Ca-containing alloys,such as Mg-2Zn-0.2Mn-0.1Ca,Mg-2Zn-0.2Mn-0.4Ca,Mg-2Zn-0.2Mn-0.7Ca,and the samples were analyzed by using a metallographic microscope,scanning electron microscopy,micro-hardness testing equipment,X-ray diffractometer.The results show that,with the increase of Ca containing,the microhardness value of Mg-2Zn-0.2Mn-xCa alloy has increased from 47.54 HV to 61.00 HV.Three different Ca content samples of Mg-2Zn-0.2Mn-xCa alloy were analyzed and tested by hydrogen evolution experiment,while the result indicates,with the increase of Ca content the average hydrogen evolution of alloy takes the trend of decreasing first and increasing second.When the Ca content is 0.4%,the alloy has the lowest average hydrogen evolution rate of 2.588ml/cm2/Day;and when the Ca content is 0.7%,the alloy has the highest average hydrogen content ofml/cm2/Day?The effects of heat treatment on the corrosion rate of Mg-2Zn-0.2Mn-0.1Ca,Mg-2Zn-0.2Mn-0.4Ca alloy have been studied.The result shows that the average hydrogen evolution of the two alloys decreases with the increase of heat treatment temperature.The average hydrogen evolution amount of Mg-2Zn-0.2Mn-0.1Ca alloy after heat treatment at 380°C and 420°C is 2.124ml/cm2/Day,and 1.538ml/cm2/Day,the relative as-casts were reduced by 28.76% and 43.77% respectively.Moreover,the average hydrogen evolution amount of Mg-2Zn-0.2Mn-0.4Ca alloy after heat treatment at 380°C and 420°C is1.489ml/cm2/Day,and 1.291ml/cm2/Day,relative to the as-cast were reduced by 42.49%,and 50.14% each.