| With the development and progress of society and living standards,people’s requirements for medical comfort are constantly improving.Magnesium alloys have gradually attracted people’s attention because of their good biocompatibility and biodegradability in vivo.Good biocompatibility can reduce patients’ discomfort symptoms such as inflammation caused by implants,and excellent in-vivo biodegradability avoids the pain of taking out implants in the second operation,and reduces the operation cost.However,although magnesium alloy can be degraded in vivo,its degradation rate is too fast and cannot be accurately controlled.In addition,during the degradation of magnesium alloy,it will generate hydrogen by displacement reaction with hydrogen ions in solution,which will lead to a series of problems such as inflammation.As a magnesium alloy implanted in human body,its surface is in direct contact with tissues,so it is necessary to have a surface that is conducive to cell climbing,growth and migration.Based on the service conditions and environment of bone plate,the surface of magnesium alloy which can be used as bone plate material was modified to improve its biocompatibility.Taking Mg-2.0Zn-1.6Ca at three different extrusion temperatures as the research object,the wear resistance of magnesium alloy at three different extrusion temperatures was investigated through fretting wear test.Through long-term immersion corrosion test and corrosion behavior observation test,the corrosion resistance of magnesium alloys at three different extrusion temperatures was investigated.The biocompatibility of magnesium alloy at different extrusion temperatures was preliminarily explored by living dead fluorescence staining test.Considering the above three aspects comprehensively,the optimal extrusion temperature is determined.CCK-8 test,leaching solution test and antibacterial test were carried out on magnesium alloy with optimal extrusion temperature to ensure that magnesium alloy was not toxic to cells.The surface of magnesium alloy was modified by laser at the optimum extrusion temperature,and the laser parameters were optimized from three aspects: frequency,speed and power.The groove morphology and field morphology with different intervals were etched on the surface of magnesium alloy,and the mechanism was explained.Through the contact angle test,the hydrophilicity and hydrophobicity of different morphologies were explored.Through cell climbing test,the effects of different morphology on cell climbing,growth and migration were explored.Fretting wear test by studying fretting friction types,friction coefficient and wear pits,it is found that with the decrease of extrusion temperature,the surface hardness increases and the friction coefficient decreases,which is very beneficial to improve the wear resistance of workpieces.Through long-term immersion corrosion test and corrosion behavior observation test,it is found that with the increase of extrusion temperature,the proportion of dynamic recrystallization increases and the corrosion resistance improves.Through the fluorescent staining test of living dead cells,it was found that magnesium alloy cells grew well at 400℃.By observing the surface morphology of sheep ribs for bionics,it is determined that the laser etching morphology is a groove.The principle of laser etching was simulated by COMSOL Mutiphysics finite element,and then the frequency,speed and power of the laser were optimized,and the groove morphology and field morphology with different intervals were etched on the surface of magnesium alloy.Finally,the morphology was evaluated by cell climbing test and contact angle test. |
