【摘要】：鎂合金由于彈性模量低、密度與人骨接近、生物相容性良好、可降解等優(yōu)點(diǎn),在生物植入材料領(lǐng)域展示了良好的應(yīng)用前景。然而純鎂及其合金在pH值為7.4～7.6、富Cl-的復(fù)雜生理系統(tǒng)環(huán)境中,腐蝕速度過(guò)快,易造成氫氣聚集導(dǎo)致植入部位的炎性反應(yīng),同時(shí)也會(huì)造成鎂合金植入物過(guò)早地失去其機(jī)械完整性,達(dá)不到服役時(shí)間要求。因此,改善鎂合金的耐蝕性并研究其腐蝕機(jī)理成為生物醫(yī)用鎂合金材料亟待解決的問(wèn)題。合金化和表面處理是兩種有效提高鎂合金耐蝕性能的方法。本文選擇Zn、Mn作為合金化元素,通過(guò)熔鑄、均勻化熱處理、正擠壓等一系列手段制備出不同錳含量的Mg-1Zn-xMn (x=0.8, 1.0, 1.2wt%)鎂合金,再采用微弧氧化工藝對(duì)鎂合金進(jìn)行表面陶瓷化處理。研究了 Mg-1Zn-xMn鎂合金進(jìn)行微弧氧化工藝處理后的微觀組織及其在SBF模擬體液中的腐蝕性能,討論了表面陶瓷膜層的組織與腐蝕性能之間的關(guān)系。得出以下主要結(jié)論:(1) Mg-1Zn-xMn合金微弧氧化陶瓷層與基體結(jié)合良好,主要相組成為MgO和Mg2Si04。陶瓷層由多孔的疏松層和致密層組成。隨著微弧氧化時(shí)間延長(zhǎng),陶瓷層缺陷增多,出現(xiàn)了較大的放電微孔。陶瓷層上存在微裂紋,是由于熔融物的不均勻冷卻造成的。(2)在相同微弧氧化工藝參數(shù)下,Mg-1Zn-0.8Mn合金微弧氧化陶瓷層的孔隙率最小,腐蝕電流密度也最小,其耐蝕性最佳。(3)表面陶瓷層可以顯著提高合金的硬度,隨微弧氧化時(shí)間增加,膜層變厚,硬度增大。微弧氧化3min (陶瓷層厚為5μm)的Mg-1Zn-1Mn合金硬度值為178HV,微弧氧化5min (陶瓷層厚為10μm)時(shí)合金硬度為274HV。微弧氧化陶瓷層可使Mg-1Zn-xMn鎂合金硬度值提高3-4倍。(4)微弧氧化可以顯著提高M(jìn)g-1Zn-xMn合金的耐腐蝕性。Mg-1Zn-1Mn合金的電化學(xué)腐蝕速率為0.252 mm/a,微弧氧化5min可使合金的腐蝕速率降低至0.026 mm/a,耐腐蝕性提高近10倍。(5)在37℃的SBF溶液中浸泡15天后,微弧氧化5 min的合金質(zhì)量損失最小,耐蝕性能最好,腐蝕以點(diǎn)蝕和絲狀腐蝕為主。合金表面的腐蝕產(chǎn)物主要由HA(Ca10(OH)2(PO4)6).MgCl2 和 Mg(OH)2 組成。
[Abstract]:Due to its low elastic modulus, close density to human bone, good biocompatibility and biodegradability, magnesium alloy has shown a good application prospect in the field of biological implant materials. However, the corrosion rate of pure magnesium and its alloys is too fast in the complex physiological system with a pH value of 7.4 ~ 7.6 and rich in Cl-, which leads to the accumulation of hydrogen and the inflammatory reaction of the implanted site. At the same time, magnesium alloy implants will lose their mechanical integrity prematurely and fail to meet the service time requirement. Therefore, improving the corrosion resistance of magnesium alloy and studying its corrosion mechanism become the urgent problem of biomedical magnesium alloy materials. Alloying and surface treatment are two effective methods to improve corrosion resistance of magnesium alloys. In this paper, Zn,Mn was chosen as alloying element. Magnesium alloys with different manganese content were prepared by melting casting, homogenizing heat treatment, forward extrusion and so on. Magnesium alloys with different manganese contents were prepared by micro-arc oxidation. The microstructure of Mg-1Zn-xMn magnesium alloy treated by micro-arc oxidation and its corrosion resistance in simulated body fluid of SBF were studied. The relationship between the microstructure and corrosion resistance of ceramic film on the surface was discussed. The main conclusions are as follows: (1) Mg-1Zn-xMn alloy ceramic coating of micro-arc oxidation binds well to the matrix, and the main phase composition is MgO and Mg2Si04.. The ceramic layer consists of porous loose layer and dense layer. With the increase of the time of micro-arc oxidation, the defects of ceramic layer increase and large discharge micropores appear. The microcracks on the ceramic layer are caused by the inhomogeneous cooling of the melt. (2) under the same process parameters of micro-arc oxidation, the porosity and corrosion current density of the ceramic layer of Mg-1Zn-0.8Mn alloy are minimum. (3) the hardness of the alloy can be improved by ceramic coating. With the increase of the time of micro-arc oxidation, the film becomes thicker and the hardness increases. The hardness of Mg-1Zn-1Mn alloy with microarc oxidation (5 渭 m ceramic layer thickness) is 178HVV, and 274HV with 5min (ceramic layer thickness 10 渭 m). (4) Micro-arc oxidation can significantly improve the corrosion resistance of Mg-1Zn-xMn alloy. The electrochemical corrosion rate of Mg-1Zn-1Mn alloy is 0.252 mm/a, 5min can reduce the corrosion rate of Mg-1Zn-xMn alloy. The corrosion resistance of 0.026 mm/a, was increased by nearly 10 times. (5) after soaking in SBF solution at 37 鈩，

本文編號(hào)：2227618