医用Mg-Zn-Gd合金微观结构与腐蚀产物分析

Corrosion behavior and microstructure of biomedical Mg-Zn-Mn-Gd alloys

背景:镁合金作为金属内固定材料,具有可降解的独特优势,且弹性模量与密质骨相近,可避免"应力遮挡"效应,但对于骨折内固定材料,生物活性代表着在体内与骨的键合能力,对其研究具有重要意义。目的:观察Mg-Zn-Gd合金的微观结构以及在模拟体液中腐蚀产物的形貌和微区分析。方法:利用熔铸合金化法制备Mg-Zn-Gd合金,扫描电子显微镜观察合金的微观组织形貌,能谱仪对微区成分和析出相进行分析。结果与结论:Mg-Zn-Gd铸态合金由含有Gd和Zn元素的过饱和α-Mg固溶体和共晶组织组成,共晶组织为羽毛状、椭圆状、鱼骨状及沿晶界分布的条状物,共晶组织主要成分为Mg、Zn和Gd;将Mg-Zn-Gd合金在Hank’s溶液中浸泡72 h后,表面沉积含有O,Mg,Ca,P元素的膜层,经XRD衍射分析,表面膜层中含有Mg(OH)_2相,该相促进含Ca盐的沉积,初步证明了镁合金具有良好的生物活性。

BACKGROUND： As a metal internal fixation material, magnesium alloy has more unique advantages, such as biodegradability and elastic modulus. The elastic modulus of magnesium alloy is similar to the compact bone, which is enough to avoid ＂stress-shelter＂ effect. However, biological activity represents bonding ability with the bone in the body for fracture fixation materials, which is of great significance for studies on new kinds ofmagnesium alloys. OBJECTIVE： To observe the microstructure of Mg-Zn-Gd alloys and to analyze the corrosion products on the material surface after immersed in simulation body fluid. METHODS： The Mg-Zn-Gd alloys were manufactured by the method of fusion casting. Scanning electron microscope with spectrometer was applied to observe microstructure and distribution of precipitated phase and corrosion products of Mg-Zn-Gd alloys in simulated body fluid. RESULTS AND CONCLUSION＂ The Mg-Zn-Gd alloy was composed of a-Mg solid solution containing Gd and Zn elements and eutectic structure. The eutectic structure was almost feathery, oval-shaped, herringbone-shaped and strip-shaped along the grain boundary. The main ingredients of eutectic structure included Mg, Zn and Gd elements. Depostion layer was composed of O, Mg, Ca and P elements on the surface of Mg-Zn-Gd alloy after 72 hours soak in Hank＇s solution. X-ray diffraction analysis showed that film layer contained Mg（OH）2 phase, which promoted calcium salt deposition and reduced the corrosion rate. So Mg-Zn-Gd alloy can obtain better biological activity.