| Magnesium alloy materials are expected to be a potential implant material duo to its unique biodegradable property and excellent mechanical compatibility,however,the high corrosion rate in biological fluid reduce the success rate of its clinical application,so improve the corrosion resistance of magnesium alloys in implanted environment,keep its mechanical integrity before the bone healing,control the degradation rate,restrict the excessive release of Mg2+,OH-and H2 corrosion products,which is the key to the biological research of magnesium alloy.This article is using biological ZK61 magnesium alloy as the matrix,adding different content of HA particles(5wt.%,10 wt.% and 15 wt.%),adopting the method of spark plasma sintering to fabricate ZK61-HA biological composite.First ZK61 magnesium alloys were sintered with different temperatures to explore densification process,and the density,structure and mechanical properties were analyzed,and determined the optimal temperature of SPS sintering magnesium alloy.Then fabricated ZK61-HA composites by SPS,researched the effect of HA particles content on microstructure,mechanical properties and in vitro degradation behavior of the composites,and explored the cytotoxic,the main conclusions are as follows:In 370,420,370 and 420 ℃ sintering temperature,the ZK61 magnesium alloy exhibited grain fine and uniform organization.The sintering process can be divided three stages: particle dense arrangement under axial pressure,block the rapid densification and composition homogenization.With the increasing of sintering temperature,the relative density of ZK61 alloy increases gradually,the largest density is 99.3% when sintered at 520 ℃ temperature.The interface bonding strength increases as the sintering temperature rises,which improved mechanical properties,compared with the alloy sintered at 370 ℃,microhardness increased by 14.6%,to 79.3 HV,compressive strength increased by 18.8%,to 304 MPa,bending strength achieved the maximum of 94.7 MPa,the compression ratio and toughness was enhanced at the same time when the sintering temperature is 520 ℃.After mixing powders,ZK61-HA composite by SPS at 520 ℃ sintering temperatures,microstructure test results show that the second phase HA ceramic particles distributed uniform around the ZK61 magnesium alloy matrix,interface bonding is good,the material inside have no obvious holes,there is no reaction between ZK61 and HA particles during SPS sintering,the phase of the composite is mainly composed of Mg and HA,the density of the composite were higher in more than 96%,with HA content increases,the relative density has a downward trend.Mechanics performance test found that the addition of the HA particles can improve the mechanical properties of the matrix alloy.The average microhardness increased by 16.5% to 93.4 HV,compress yield strength increased by 15.6% to 230 MPa,the bending modulus achieved maximum of 31.5 GPa when HA content at 15wt%,the compressive strength increased from 0wt% of 304 MPa to 10wt% 429 MPa,bending strength was uping to 142.7 MPa in 5wt.%.Electrochemical polarization behavior test of the composite showed that the electrochemical corrosion mechanism of similar material in SBF solution,the addition of HA particles can improve the electrochemical corrosion properties of the matrix alloy,when HA content in 10 wt.%,the corrosion potential achieved maximum of-1.5327 V,the corrosion current achieved minimum of 1.83x10-4 a/cm2.Soaking behavior found that: with the addition of HA particles,the hydrogen evolution of the composite and the p H value of solution were reduced,the weightlessness corrosion rate was lower than those of the magnesium alloy substrate also,ZK61-10 HA composite has lowest average immersion corrosion rate of 14.9 mm/y,exhibited good corrosion resistance.With determined by MTT colorimetric method for ZK61-HA composite cytotoxicity test results found that L-929 cell growth in the leaching solution of composite material is in good condition,cell toxicity ratings are qualified. |
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