| Biomedical materials have been researched widely in recently years. Studies about biomaterial have become one of the hottest and most important research fields in life science. Currently approved and commonly used biomedical metal materials include stainless steels, cobalt-based alloys, titanium and titanium alloy. But those materials would also cause the stress shielding effects, the release of toxic metallic ions and some chronic inflammation under physiological environment. Most of current metallic biomaterials are inert in vivo, remaining as permanent implants, which must be removed by a second surgical operation.Magnesium alloys have been suggested for implant materials due to their well biocompatibility, biodegradability and density and elastic modulus which are so closed to that of human femur bone. But magnesium alloy has a active chemical properties, lead to extremely fast corrosion rate in the complicated environment of human body, which seriously restrict its application in biomaterial. This work is mainly adding Ca element into ZM61 alloy to improve its corrosion resistance, in order to achieve the biomaterial application requests.ZM61 alloy and Mg-30Ca alloy are used to prepare the Mg-6Zn-Mn-x(x=0, 0.3, 0.5, 1.0)Ca alloys. The influence of Ca content to the microstructure and properties of ZM61 alloy were investigated through optical microscopy, XRD, scanning electronic microscopy (SEM) and electrochemical measurement and the best Ca content were selected out. The influence of heat treatment to the selected alloy's microstructure and properties were studied then. The results showed that:(1)The grain size of as-cast of ZM61-XCa alloy was decreased with the increase of Ca content, and when the Ca content reached 1.0%, the grain size was decreased visibly.(2)The phase composition of the as-cast of ZM61-1.0Ca alloy was composed ofα-Mg, dendrite Ca2Mg6Zn3, eutectic (α-Mg + Ca2Mg6Zn3) and Mn-containing particles.(3)The corrosion resistance of the as-cast of ZM61-XCa alloy was improved with the increase of Ca content, but then decreased,and ZM61-0.5Ca showed the best corrosion resistance.(4)The microstructure of ZM61-0.5Ca alloy was changed significantly after annealing and solution treatment,the number of dendritic crystal was decreased after annealing; There was some flake phases in trigonal grain boundary , and some Mg2Ca phases were arise after aging treatment.(5)The result of electrochemical test shows that the Ecorr were very closed with different heat treatment sates, and the ZM61-0.5Ca alloy has the best corrosion resistance by 180℃aging 8h. |
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