| As a common cardiovascular disease,coronary heart diseaseis seriously harmful to human health.Stent implantation is an effective method to treat coronary heart disease.Magnesium and its alloys are ideal for stent implantation because of their excellent biodegradability in vivo,mechanical compatibility and biocompatibility.However,the excessively fast degradation rate restricts its clinical application.This article aims to develop a biomagnesium alloy for cardiovascular scaffolds with good corrosion resistance,and evaluate its mechanical properties as well as biocompatibility so as to provide reference and support for the research and development of other new biomagnesium alloys.According to the previous work of the research group,in this experiment,Mg-2Y-1Zn-0.4Zr-0.3Sr alloy is smelted by adding elements Y,Zn,Zr and Sr with good biocompatibility.The as-cast alloy is solution heat-treated(500?,25 h),followed by hot extruded(400?,16:1,1 mm/s)to obtain magnesium alloys in different conditions.The corrosion resistance,mechanical properties and biocompatibility of Mg-2Y-1Zn-0.4Zr-0.3Sr alloy are tested via XRD,OM,SEM&EDS,electrochemistry,mass loss testing,room temperature tensile,microhardness,hemocompatibility and cytocompatibility.Mg-2Y-1Zn-0.4Zr-0.3Sr alloy is mainly composed of ?-Mg matrix and Mg3Y2Zn3(W)phase.The W-phase of the as-cast alloy which is(semi-)continuous is mainly distributed on the grain boundary.The volume fraction and size of W-phase that became completely discontinuous at the grain boundary are reduced significantly by solution heat-treatment.After hot extrusion,the W-phase with decreased size and volume fraction is dispersed along the extrusion direction,and the grain is refined obviously.The corrosion rate of the as-cast alloy is higher than that of pure magnesium due to the large amount of W-phase.Solution heat-treatment and hot extrusion can significantly improve the corrosion resistance of the alloy.The mass loss results show that the corrosion rates of the pure magnesium,as-cast,solution heat-treated and as-extruded alloys after immersion in the simulated body fluid for 240 h are 0.0624 mg·cm-2·h-1,0.0758 mg·cm-2·h-1,0.0545 mg·cm-2·h-1,0.0432 mg·cm-2·h-1,respectively.The galvanic corrosion caused by the potential difference between?-Mg matrix and W-phase is the main corrosion type of Mg-2Y-1Zn-0.4Zr-0.3Sr alloy.W-phase volume fraction,size,distribution,grain size and defects are the main factors affecting the corrosion resistance of Mg-2Y-1Zn-0.4Zr-0.3Sr alloy.Compared with pure magnesium,the as-cast Mg-2Y-1Zn-0.4Zr-0.3Sr alloy has a significant increase in room temperature tensile properties and microhardness,which is attributed to solution strengthening,precipitation strengthening and fine-grain strengthening caused by casting processing.Solution heat-treatment can weaken the effect of precipitation strengthening and fine-grain strengthening,and reduce the comprehensive mechanical properties.The main reason for the good mechanical properties of the as-extruded alloy is the large decrease of grain size after hot extrusion.The results show that the as-extruded alloy has the best mechanical properties,and the ultimate tensile strength(UTS),yield strength(YS),elongation(E)and Vickers hardness(HV)are 254 MPa,195 MPa,27.0%,and 68.19±3.01,respectively.Pure magnesium and Mg-2Y-1Zn-0.4Zr-0.3Sr alloy have good blood compatibility and cytocompatibility,and are closely related to the corrosion rate.In a short time(<72h),the relative growth rate of L929 cells in pure magneisum and alloys extracts have little change,and there is no obvious time dependence.Results show that the as-extruded alloy has the best biocompatibility. |
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