关键词： AZ31镁合金   孪生   织构   高应变速率   变形机制  

摘要： 采用分离式霍普金森压杆(SHPB)测试预孪晶AZ31镁合金板材在应变速率分别约为800、1200和1600 s−1时的动态真应力−真应变曲线。通过自编程软件及电子背散射衍射(EBSD)技术分析预孪晶试样在高应变速率前后微观组织和织构的演变。结果表明:沿横向(TD)预压缩后再沿着轧制方向(RD)复合预压缩可促进AZ31镁合金板材中多孪晶变体及二次拉伸孪晶的激活。对于沿TD方向一次预压缩的试样,其法向(ND)高应变速率下的屈服强度急剧下降,这主要是由于退孪生的启动。然而,对于沿TD+RD复合预压缩试样,由于{1012}−{1012}二次孪晶和大量交叉孪晶变体的形成可以有效抑制退孪生行为,一定程度上提高了AZ31镁合金ND方向的屈服强度,并且拉伸孪晶的形成能够便利于启动更多的滑移系,改善了镁合金板材ND方向的塑形变形行为。

关键词： 镁合金   微弧氧化   配方均匀试验   电解液   微观组织   耐蚀性  

摘要： 目的研究电解液中各电解质不同浓度配比下微弧氧化膜层的制备、微观结构及耐蚀性能,以确定最优配方。方法基于配方均匀试验方法,在硅酸盐系电解液中对AM60B镁合金进行微弧氧化处理。引入微弧氧化反应的可行性和微弧氧化膜层的成膜性两个试验指标,分别评判本研究中某电解液配方是否具有实际应用价值,以及评价在某个电解液配方下所制得膜层的合格程度。利用涡流测厚仪、扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)、硝酸点滴实验以及电化学实验等方法,分别表征膜层的厚度、微观结构、物相组成、元素成分及耐蚀性能。结果当电解液中NaOH的质量浓度小于10 g/L时,方能获得表观完整且色泽均匀的微弧氧化膜层。当NaOH和KF的浓度配比接近,且两者之和约为Na_(2)SiO_(3)所占配比时,即Na_(2)SiO_(3)为19.24 g/L、NaOH为8.80 g/L、KF为11.96 g/L时,膜层中孔径的尺寸小,缺陷少,致密度最高,此时膜层的耐蚀性最好,与基体相比,该膜层的硝酸点滴耐蚀性提高了39倍,电化学耐蚀性提高了3个数量级。膜层主要由MgO、Mg_(2)SiO_(4)及少量的MgF_(2)、MgAl_(2)O_(4)组成,但含量有差别。结论实验设计方法的选择是保证本研究结果有效性的核心和关键。电解液中NaOH的浓度高低是决定某电解液配方是否具有实用价值的首要因素。只有Na_(2)SiO_(3)、NaOH和KF三者间具备适当的配比时,才能降低膜层中的微孔尺寸,减少微裂纹,提高其致密度,并能够在膜层中沉积更多的优质物相,这些是增强膜层耐蚀性的前提和保障。

关键词： 镁合金   成分   组织   高温氧化   阻燃  

摘要： 镁合金具有低密度、高比强度和比刚度,是交通运输领域潜在的轻质结构材料。然而,镁合金的抗高温氧化性差和易燃性限制了其应用。本文详细介绍了镁合金在空气中高温氧化与燃烧的基本原理以及镁合金高温氧化的影响因素;总结了镁合金高温氧化与阻燃研究进展,包括目前已提出的镁合金抗氧化模型理论,与Ca、Be、Sr和稀土等元素合金化的镁合金阻燃机理;提出了阻燃镁合金在发展过程中遇到的一些问题,并指出其可能的发展方向。

关键词： Aluminum   Magnesium   Polarization   EIS   Alkaline corrosion   Galvanic corrosion  

摘要： The corrosion behavior and corrosion rate of friction stir welded AZ31B magnesium alloy and 6N01 aluminum alloy dissimilar joints were studied using real-time imaging, potentiodynamic polarization, EIS, and hydrogen evolution tests. The corrosion rate was found to increase, in order, Al base metal (BM-6N01) < Mg base metal (BM-AZ31B) < stirred zone. The galvanic coupling of the Mg phase to the other phases enhanced the corrosion of both BM-AZ31B and BM-6N01. Accompanying the intense corrosion at BM-AZ31B, water reduction on the cathodic particles of BM-6N01 elevated the interfacial pH to a level where the Al matrix corroded to AlO2-.

关键词： Magnesium alloy   Blood compatibility   Anticorrosion   Endothelial cell   Antibacterial  

摘要： Magnesium alloy represents one of the most potential biodegradable vascular stent materials due to its good biodegradability, biocompatibility and suitable mechanical properties, whereas the rapid degradation in physiological environment and the limited biocompatibility remain the challenges. In this study, graphene oxide (GO) was firstly functionalized by chitosan (GOCS), followed by loading zinc ions and propranolol to obtain GOCS@Zn/Pro complex, which was finally covalently immobilized on the self-assembled modified magnesium alloy surface to enhance the corrosion resistance and biocompatibility. The multi-functional coating can significantly improve the corrosion resistance and reduce the degradation rate of the magnesium alloy. Furthermore, the coating can significantly inhibit platelet adhesion and activation, reduce hemolysis rate, prolong activated partial thromboplastin time (APTT), and thus improve the blood compatibility of the magnesium alloy. In addition, the modified magnesium alloy can not only significantly promote the endothelial cell adhesion and proliferation, up-regulate the expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO), but also endow the materials with good antibacterial properties. Therefore, the method of the present study can be used to modify magnesium alloy stent materials to simultaneously enhance corrosion resistance and blood compatibility, promote endothelialilization, and inhibit infections.

关键词： Anti-corrosion   Superhydrophobic surface   Magnesium alloys  

摘要： A bilayer coating superhydrophobic surface was developed by a simple one-step solvothermal method. This strategy can realize the introduction of low surface energy myristic acid/n-dodecyltrimethoxysilane and the fabrication of complex bionic micro/nano structure in one step, thereby further simplifying the manufacturing process. The as-obtained superhydrophobic surface has a CA of 157.6 degrees and a SA of 2.0 degrees. The bionic micro/nano structures are like the common herb sowthistle. The bilayer coating superhydrophobic surface has excellent self-cleaning properties, chemical stability and corrosion resistance. In addition, this strategy can effectively broaden the application of magnesium alloys and extend to other conductive metal materials.

关键词： Magnesium alloys  

摘要： Magnesium (Mg) has a strong application potential as a lightweight metal. Yet, its absolute strength still needs improvement. In this work, we demonstrate that machine learning can be utilized to guide the development of high-strength Mg cast alloys. In the design framework, the composition and heat treatment condition are iteratively optimized by a surrogate model that is also evolving. After two iterations, a new alloy with the composition of Mg-10.0Al-2.0Sn-2.0Zn-0.1Ca-0.1Mn (at. pct) was identified. After aging at 200 degrees C for 96 hours, this alloy shows a Vickers hardness value of 110.5 Hv, which surpasses the highest value (102.5 Hv) in the initial dataset from literature. Finally, microstructure of the optimized alloy was characterized to understand the origin of its high hardness. This work demonstrates the potential of data-driven approaches for material development.

关键词： corrosion behavior   EIS   magnesium alloy   orientation   simulated body fluid  

摘要： Two orientation samples were prepared along the normal (ND) and transverse (TD) directions of the rolled AZ80 magnesium alloy. The samples (ND and TD) were immersed in simulated body fluid (SBF) for long-term (25 days) immersion test. Electrochemical measurements such as electrochemical impedance spectroscopy and potentiodynamic polarization test were conducted to study the electrochemical behavior. Scanning electron microscopy and energy-dispersive x-ray spectrometer were used to investigate the corrosion morphology and chemical composition of samples during various immersion processes. X-ray diffraction was employed to identify the texture composition. The results indicated that severe localized corrosion occurred in the ND sample. Uniform corrosion was the dominant corrosion in the TD sample. The TD sample exhibited better corrosion performance (higher corrosion resistance and lower corrosion rate) than the ND sample. The corrosion behavior of magnesium alloy was closely related to texture, microstructure, and corrosion product film. The influence mechanism of texture and microstructure on corrosion behavior of magnesium alloy was discussed.

关键词： Magnesium alloys  

摘要： The in vivo fast degradation and poor biocompatibility are two major challenges of the magnesium alloys in the field of artificial bone materials. In this study, graphene oxide (GO) was first functionalized by chitosan (GOCS) and then immobilized on the magnesium alloy surface, finally the complex of heparin and bone morphogenetic protein 2 was incorporated on the modified surface to synergistically improve the corrosion resistance, anticoagulation, and osteogenesis. Apart from an excellent hydrophilicity after the surface modification, a sustained heparin and BMP2 release over 14 days was achieved. The corrosion resistance of the modified magnesium alloy was significantly better than that of the control according to the results of electrochemical tests. Moreover, the corrosion rate was also significantly reduced in contrast to the control. The modified magnesium alloy not only had excellent anticoagulation, but also can significantly promote osteoblast adhesion and proliferation, upregulate the expression of alkaline phosphatase and osteocalcin, and enhance mineralization. Therefore, the method of the present study can be used to simultaneously improve the corrosion resistance and biocompatibility of the magnesium alloys targeted for the orthopedic applications. [GRAPHICS] . Highlights The GOCS@Hep/BMP2 bioactive coating was created on the magnesium surface. The coated magnesium alloy had good wettability and corrosion resistance. The coating can improve anticoagulation and osteogenesis of magnesium

关键词： Composite coatings  

摘要： The bacterial infection of bone implants is a vital factor leading to implant failure. Superhydrophobic surface with low adhesion can effectively enhance corrosion resistance and antibacterial adhesion properties of magnesium alloy. Herein, the superhydrophobic composite coating of hydroxyapatite (HA)/stearic acid was successfully prepared on magnesium alloy (AZ31B) using hydrothermal method and followed modification of stearic acid. The wettability, corrosion resistance and antibacterial adhesion capacity of the composite coating were studied. The composite coatings confer excellent superhydrophobicity with a contact angle about 152.52 degrees and a sliding angle about 2 degrees, and showed good long-term superhydrophobic stability in air. Meanwhile, during immersion in simulated body fluid (SBF), the superhydrophobic composite coating was converted to hydrophilicity in a short time and exposed the micro-/nano-scale structure surface of HA, which could induce the fast deposition of the mineralized apatite layer. The characteristics endowed the composite coating with the short-term antibacterial adhesion property and long-term corrosion resistance in SBF, which will afford a surface modification strategy for the application of magnesium alloy implants in orthopedics and dentistry.