合金元素Nd对AZ系镁合金牺牲阳极材料耐腐蚀和电化学性能的影响

目前,关于稀土元素Nd对镁合金阳极耐腐蚀性和电化学性能影响的报道较少。向AZ31和AZ63镁合金中加入稀土元素Nd,测试了AZ31和AZ63镁合金加入Nd元素前后在3.5%NaCl溶液中的静态析氢腐蚀速率、失重腐蚀速率、极化曲线和电流效率,观察了镁合金试样的显微组织与腐蚀形貌;研究了合金元素Nd对AZ31、AZ63镁合金牺牲阳极的耐腐蚀与电化学性能的影响。结果表明:合金元素Nd的加入能使AZ31、AZ63镁合金晶粒细化、组织均匀,自腐蚀速率降低、电流效率提高;加入Nd元素后,AZ31,AZ63镁合金的阳极极化没有明显增加。     

Nd对AZ91镁合金组织和高温力学性能的影响

研究了Nd对AZ91镁合金组织和高温力学性能的影响.结果表明,稀土Nd(1%～4%(wt))的加入明显细化了AZ91镁合金的铸态组织,减少了β(Mg17Al12)相的析出.随着稀土Nd含量的增加,室温、150℃和250℃等3个温度下的强度都是先升后降,Nd含量为1%时合金的强度均达到最大值,特别是150℃下其强度高达203MPa;Nd含量的增加对AZ91镁合金的延伸率影响规律也是先升后降,高温下当Nd含量为2%时合金的延伸率达到最大值,表现出良好的韧性,同时也具有较高强度.     

Nd、Y对AZ31镁合金热轧退火薄板耐蚀性的影响

为提高AZ31镁合金热轧退火薄板的耐蚀性,本实验在合金中分别添加单一Nd和复合Nd+Y稀土元素,采用盐雾腐蚀和电化学腐蚀实验方法对其耐蚀性展开研究,并利用扫描电镜(SEM)、X射线衍射(XRD)仪对合金和腐蚀产物的微观组织及结构进行观察分析。结果表明:添加稀土元素Nd、Y后,AZ31镁合金表面可形成更为耐蚀的含有稀土氧化物Nd_2O_3的腐蚀产物膜,提高对基体的保护作用;添加Nd、Y元素的AZ31镁合金中新的耐蚀相Al_2Nd和Al_2Y析出,有害相β-Mg_(17)Al_(12)减少,使合金自腐蚀电位正移,腐蚀电流密度减小,腐蚀速率减缓,耐蚀性明显提高;复合添加Nd+Y比单一添加Nd更有利于提高AZ31镁合金的耐蚀性,且添加量为0.5%Nd+0.5%Y时合金的耐蚀性能提高最为显著。     

稀土Ce和Nd对AZ31镁合金耐蚀性能的影响

采用盐雾腐蚀和动电位扫描研究了稀土元素Ce、Nd对AZ31镁合金耐腐蚀性能的影响.采用数码相机、金相显微镜和扫描电镜观察及定量金相分析系统测量分析了样品的腐蚀程度,并采用恒电位仪测量了动电位扫描极化曲线.结果表明,盐雾腐蚀试验中,合金试样腐蚀面积百分数随时间延长呈直线上升,添加稀土Ce和Nd后腐蚀速率降低50%以上.在电化学试验中.添加稀土后合金腐蚀电流密度降低了1/3～1/2.稀土可以起到提高α(Mg)固溶体耐蚀性能的作用,还可以形成含稀土的第二相并使AZ31合金中的β(Mg17Al12)相均匀分布,发挥其阻碍腐蚀的作用,从而最终提高AZ31镁合金的耐蚀性能.     

微量稀土Nd对AZ91微观组织及腐蚀性能的影响

采用X-射线衍射(XRD)、扫描电镜(sEM)、能谱分析(EDS)、集气法、动电位极化及浸泡实验等手段和方法研究了添加微量稀土元素钕(Nd)对AZ91镁合金微观组织及耐蚀性的影响,并从热力学角度分析了Nd对提高合金耐蚀性的影响机制.结果表明.少量稀土Nd细化了合金的微观组织,使β-Mg17Al12相变得断续、弥散,生成了Al3Nd相及Mg-Al-Mn-Nd-Fe金属问化合物;稀土Nd使合金在3.5%NaCl溶液中的自腐蚀电位升高,且与Al、O生成了不连续的致密的氧化膜,提高了合金的耐腐蚀性能;添加1.0wt%Nd时合金的耐蚀性最佳,腐蚀速率为0.28 mg·cm-2·d-1,比AZ91合金下降了一个数量级.     

AZ31镁合金的研究现状和发展前景

叙述了AZ31镁合金在组织、性能等方面的特点,介绍了主要合金元素对AZ(Mg-Al-Zn)系镁合金组织和性能的影响;综述了该合金的研究现状,提出了该合金发展和应用前景.     

稀土Gd对AZ31镁合金耐蚀性能的影响

利用失重法研究不同Gd含量的AZ31镁合金在3.5%(质量分数,下同)Na2SO4溶液中的腐蚀行为,并采用OM,SEM和XRD等检测手段分析稀土Gd对AZ31镁合金微观组织、腐蚀速率和腐蚀形貌等的影响。结果表明:稀土Gd的添加能明显改善AZ31镁合金的耐蚀性能,且当Gd的添加量小于4.12%时,合金的耐蚀性能会随着Gd含量的增加而提高,但继续增大Gd含量时合金的耐蚀性能反而会出现一定程度的下降,其原因是合金中添加过多的Gd后,加剧了基体相与析出相之间的微电偶腐蚀,致使合金的耐蚀性能有所下降。故当Gd的添加量为4.12%时,AZ31镁合金的耐蚀性能最佳。     

AZ31镁合金钕基转化膜工艺与耐蚀性能研究

研究了AZ31镁合金钕基转化膜的制备工艺,并对膜层形貌、化学组成和耐腐蚀性能进行了分析。通过正交优化得到了钕基转化膜的4个工艺条件的最佳水平组合为Nd(NO3)3浓度为5g/L,H2O2浓度为5mL/L,成膜时间9min,成膜温度40℃。结果表明,采用最佳工艺得到的钕基转化膜层均匀且致密,其主要成分是Nd2O3和少量MgO。通过动电位极化曲线和析氢实验研究了钕基转化膜层对AZ31镁合金在3.5%(质量分数)NaCl溶液中耐蚀性能的影响,结果表明,钕基转化膜可以大大降低AZ31镁合金的腐蚀速率,当Nd(NO3)3浓度为5g/L时,钕基转化膜的腐蚀电流密度最小,耐腐蚀性能最好。     

塑性变形对铸态AZ31镁合金组织和性能的影响

为了研究塑性变形对铸态镁合金组织和性能的改善作用,用铸态AZ31镁合金进行了等温压缩实验,并测试了原始试样和变形后试样的组织和性能.结果表明:铸态AZ31合金通过塑性变形可以显著细化晶粒;随变形温度的升高,变形所得试样抗拉强度下降;在同一温度下变形所得试样抗拉强度随变形程度的增加而升高,变形程度达到一定值后,抗拉强度不再升高并有下降的趋势;铸态AZ31合金低温变形(210～240℃)后,可大幅度提高其抗拉强度.     

AZ91铸态镁合金中Mn含量对其微观组织及耐蚀性能的影响

目前,关于Mn对AZ91铸态镁合金耐蚀性能影响的研究并不充分,尤其是腐蚀机制方面仍不清楚。采用静态失重、电化学及盐雾腐蚀法研究了Mn含量对AZ91铸态镁合金微观组织及耐腐蚀性能的影响。利用金相显微镜(OM)、扫描电镜(SEM)观察AZ91铸态镁合金的微观组织和腐蚀形貌,采用能谱(EDS)仪、X射线衍射仪(XRD)分析了其物相组成。结果表明:AZ91铸态镁合金中的Mn主要以颗粒状的低电化学活性物质Al2Mn形式存在,阻碍了其腐蚀过程的进行;Mn能使AZ91铸态镁合金中的有效腐蚀相β-Mg17Al12减少,分布更弥散,从而使合金的腐蚀电位升高,腐蚀电流降低,腐蚀速率降低,耐腐蚀性能增强;含0.8%Mn的铸态镁合金的耐腐蚀性能最好。     

激光熔化镁合金凝固组织及腐蚀行为

采用Nd:YAG毫秒脉冲激光器,在高纯氩气保护下扫描AZ91D镁合金样品,采用X射线衍射仪(XRD),光学显微镜,扫描电镜(SEM),原子力显微镜(AFM)等对处理后镁合金表面形貌、组织、成分进行研究。使用模拟改性体液和质量分数为3.5%的NaCl溶液对实验样品进行腐蚀,观察腐蚀表面并计算材料腐蚀率。结果表明:在相同腐蚀时间下,与未被处理样品相比,激光处理后镁合金由于其显微组织中细化的α-Mg相与β-Mg_(17)Al_(12)相,及选择性气化现象和基体合金化学成分共同导致表面Al元素富集提高了表层的抗腐蚀性能;通过测算激光熔化区枝晶晶胞尺寸与冷却速率的关系得到其凝固方程。     

Evaluating the improvement of corrosion residual strength by adding 1.0 wt.% yttrium into an AZ91D magnesium alloy

The influence of yttrium on the corrosion residual strength of an AZ91D magnesium alloy was investigated detailedly. Scanning electron microscope was employed to analyze the microstructure and the fractography of the studied alloys. The microstructure of AZ91D magnesium alloy is remarkably refined due to the addition of yttrium. The electrochemical potentiodynamic polarization curve of the studied alloy was performed with a CHI 660b electrochemical station in the three-electrode system. The result reveals that yttrium significantly promotes the overall corrosion resistance of AZ91D magnesium alloy by suppressing the cathodic reaction in corrosion process. However, the nucleation and propagation of corrosion pits on the surface of the 1.0 wt.% Y modified AZ91D magnesium alloy indicate that pitting corrosion still emerges after the addition of yttrium. Furthermore, stress concentration caused by corrosion pits should be responsible for the drop of corrosion residual strength although the addition of yttrium remarkably weakens the effect of stress concentration at the tip of corrosion pits in loading process.     

Effect of neodymium on microstructure and corrosion resistance of AZ91 magnesium alloy

The corrosion behavior of a new Mg–9Al–1Zn (AZ91) magnesium alloy containing neodymium (Nd) is investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), immersion tests and electrochemical experiments. The results indicate that Nd decreases the size and volume fraction of the β (Mg₁₇Al₁₂) phase and forms Al₂Nd in the alloy. In addition, during corrosion, Nd is incorporated into corrosion film in the form of Nd₂O₃. AZ91 alloy containing 1.0 wt.% Nd possesses an outstanding passivation property and excellent corrosion resistance. The corrosion resistance enhancement is attributed to the reduction in the size and volume fraction of the β phase and the incorporation of Nd₂O₃ in the corrosion film.     

AZ91D镁合金化学镀Ni-P/Ni-W-P双层镀层研究

为了提高镁合金的耐磨耐蚀性,研究了一种镁合金直接化学镀Ni-P/Ni-W-P双层镀层的方法.采用扫描电镜(SEM)和X-射线衍分析射仪(XRD)分析了镀层的微观结构.对镀层进行了极化曲线分析,并进行了盐酸腐蚀试验和结合力试验.结果表明,该复合镀层组织致密无孔,具有较高的显微硬度和高耐蚀性.镀层硬度可达622HKV,试样在10%的HCl溶液中可保持近3h不腐蚀基体,对镁合金起到很好的保护作用.     

Biocorrosion resistance of coated magnesium alloy by microarc oxidation in electrolyte containing zirconium and calcium salts

The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property on AZ91D alloy by microarc oxidation （MAO） in a silicate-K2ZrF6 solution with and without Ca（H2PO4）2 additives. The microstructure and biocorrosion of coatings were characterized by XRD and SEM, as well as electrochemical and immersion tests in simulated body fluid （SBF）. The results show that the coatings are mainly composed of MgO, Mg2SiO4, m-ZrO2 phases, further Ca containing compounds involve the coating by Ca（H2PO4）2 addition in the silicate-K2ZrF6 solution. The corrosion resistance of coated AZ91D alloy is significantly improved compared with the bare one. After immersing in SBF for 28 d, the Si-Zr5-CaO coating indicates a best corrosion resistance performance.     

AZ91 Magnesium Alloy/Porous Hydroxyapatite Composite for Potential Application in Bone Repair

AZ91/HA composite was prepared by AZ91 magnesium alloy and porous HA using squeeze casting method.The microstructure and mechanical property of the AZ91/HA composite were studied. The results show that the molten AZ91 alloy completely infiltrated the preform without destroying the porous structure of the HA preform. The compressive strength of AZ91/HA composite increased significantly compared with that of the porous HA. The immersion test indicated that AZ91 alloy shows a lower corrosion resistance and is easier to be corroded in comparison with HA.     

镁合金表面喷铝防腐蚀层的微观组织分析

在AZ91D镁合金表面热喷铝，用以提高其表面的耐腐蚀性能。采用SEM，EPMA等方法对AZ91D表面喷铝扩散层的组织进行了仔细的观察与分析，发现在防腐蚀层上有大量的Mg17Al12相存在，且呈决状及非连续片状分布。经显微硬度测定，喷铝层硬度较镁合金基体高；腐蚀后这种相凸出于基体，比镁合金基体有较好的耐腐蚀性能。     

Laser cladding of Zr-based coating on AZ91D magnesium alloy for improvement of wear and corrosion resistance

To improve the wear and corrosion resistance of AZ91D magnesium alloy, Zr-based coating made of Zr powder was fabricated on AZ91D magnesium alloy by laser cladding. The microstructure of the coating was characterized by XRD, SEM and TEM techniques. The wear resistance of the coating was evaluated under dry sliding wear test condition at room temperature. The corrosion resistance of the coating was tested in simulated body fluid. The results show that the coating mainly consists of Zr, zirconium oxides and Zr aluminides. The coating exhibits excellent wear resistance due to the high microhardness of the coating. The main wear mechanism of the coating and the AZ91D sample are different, the former is abrasive wear and the latter is adhesive wear. The coating compared to AZ91D magnesium alloy exhibits good corrosion resistance because of the good corrosion resistance of Zr, zirconium oxides and Zr aluminides in the coating.     

AZ31镁合金表面激光熔覆Al-TiC复合涂层微观组织与腐蚀性能

为有效改善AZ31镁合金表面的腐蚀性能，本文采用激光熔覆技术在AZ31镁合金表面成功制备了无缺陷的Al-TiC复合涂层。研究了不同成分含量的Al-TiC复合涂层的相组成、微观组织和耐腐蚀性能的影响。结果表明：在Al-TiC复合涂层内形成了大量的Al₁₂Mg₁₇、Mg₂Al₃和TiC相。复合涂层内微观组织呈现出连续网络状分布特征。随着Al-TiC混合粉末中Al含量的减小，复合涂层中Al₁₂Mg₁₇、Mg₂Al₃和TiC相的含量呈递增趋势，网络状分布的微观组织结构变得更加均匀连续。复合涂层与AZ31基体之间形成了良好的冶金结合界面。激光熔覆制备的Al-TiC复合涂层耐腐蚀性能较AZ31基体显著提升。自腐蚀电位由基体的-1.563 V提升至-1.144 V，自腐蚀电流由基体的1.55×10^-4 A减小至2.63×10^-6 A。     

镁合金微弧氧化陶瓷膜的微观结构、相成分和耐腐蚀性能

为获得耐腐蚀性优良的镁合金表面膜层,在含5 g/L硅酸钠、2 g/L磷酸钠和1 g/L氢氧化钠的复合溶液中,用自制设备对AZ91D镁合金进行了微弧氧化.利用扫描电镜和X射线衍射分析了AZ91D 镁合金表面微弧氧化陶瓷膜的表面形貌、截面结构和相组成.结果表明:AZ91D 微弧氧化陶瓷膜由疏松层和致密层组成,疏松层陶瓷膜疏松,厚度较大,且存在一些孔洞;致密层陶瓷膜与基体金属结合紧密,陶瓷膜主要由MgO,Mg2SiO4,Mg3(PO4)2和MgAl2O4组成.在3.5%的NaCl溶液中,微弧氧化陶瓷膜的自腐蚀电位为-1 390 mV,而镁合金基体的为-1 540 mV,表明经微弧氧化处理后AZ91D 镁合金的耐蚀性有较大提高.