稀土铈对AZ91镁合金表面腐蚀性能的影响

为解决镁合金表面处理工艺复杂、成本高且存在环境污染问题 ,采用气相扩渗法研究了稀土铈对AZ91镁合金表面的渗入及其耐腐蚀性能的影响 .结果表明 ,经过扩渗稀土铈表面处理的AZ91镁合金 ,腐蚀电阻增大近一倍 ,均匀腐蚀速率由 1.85 0mg/m2 ·s降为 0 .876mg/m2 ·s;腐蚀电位正移 ,同一电位下所对应的腐蚀电流密度明显降低 .利用X射线光电子能谱 (XPS)分析了经过扩渗稀土后AZ91镁合金表面的成分中 ,稀土铈是以化合态的形式存在于表层 ,渗入的稀土元素铈起到净化合金表面、微合金化的作用     

T6处理对真空压铸AM50镁合金腐蚀行为的影响

为了研究不同时效工艺对真空压铸AM50镁合金耐蚀性的影响,通过静态失重实验和电化学实验研究了T6处理后AM50镁合金在Na Cl溶液中的腐蚀行为.结果表明,合金经过170和230℃时效处理后腐蚀速率的变化情况基本类似,均为先降低后升高,最后达到一个稳定值.但经过230℃时效处理后合金的耐蚀性远差于经过170℃时效处理后的情况,且达到腐蚀速率最低点所需时间更长.不同时效处理后的合金具有相似的电化学腐蚀行为,腐蚀电位无明显变化规律,而腐蚀电流密度与腐蚀速率的变化趋势近乎一致.腐蚀速率随腐蚀时间的延长而下降,并最终保持一个较为稳定的数值.此外,合金腐蚀速率的理论值和实测值相吻合.     

Galvanic corrosion behavior of die cast AZ91D magnesium alloy in chloride solution

The galvanic corrosion behavior of die cast AZ91D magnesium alloy coupled with H62 brass, 316L stainless steel, A3steel and LY12 aluminum alloy of different areas in 3.5% NaC1 solution was studied. The free corrosion potentials, galvanic potentials and currents of these galvanic couples were measured. The galvanic effects were determined by the mass loss and regression method using three points. The results show that: (1) In these four kinds of couples AZ91D acts as the anode, whose galvanic corrosion behavior is mainly controlled by the cathodic polarization; (2) The free corrosion potentials of these four kinds of couples change a liffle with time and cathodic/anodic area ratio (CAAR); (3) The galvanic potential of AZ91D/LY12 moves positively with the increase of time and CAAR; (4) The galvanic currents increase with CAAR, but there is difference in the current change between different couples; (5) The anodic dissolution rate of the magnesium alloy increases by 2-3 orders after being coupled with these four kinds of metals and the galvanic effects of these couples have such a relation as γH62＞γ316LS.S＞γLY12 ＞γA3.     

Behavior of stress corrosion cracking in a magnesium alloy

Slow strain rate testing (SSRT) was employed to study the stress corrosion cracking (SCC) behavior of ZE41 magnesium alloy in 0.01 M NaCl solution. Smooth tensile specimens with different thicknesses were strained dynamically in both longitudinal and transverse direction under permanent immersions at a strain rate of 10⁻⁶ s⁻¹. It is found that ZE41 magnesium alloy is susceptible to SCC in 0.01 M NaCl solution. The SCC susceptibility of the thinner specimen is lower than that of the thicker specimen. Also, the longitudinal specimens are slightly more susceptible to SCC than the transverse specimens. The SCC mechanism of magnesium alloy is attributed to the combination of anodic dissolution with hydrogen embrittlement. Funded by the National Natural Science Foundation of China (No. 50771093)     

Ho对AZ91镁合金腐蚀行为的影响

采用重力铸造方法制备了3种Ho改性AZ91镁合金。通过腐蚀实验对改性合金的自腐蚀和电偶腐蚀行为进行了研究。结果表明,随着Ho含量的增加,改性合金的自腐蚀性能和电偶腐蚀性能逐步提高,当Ho的质量分数为1.10%和2.16%时,合金的耐蚀性能较佳。此外,阴极的特性对改性合金的腐蚀性能有明显影响,4种材料的阴极作用由弱到强依次为:铝硅合金,纯铝,45#钢和球墨铸铁。Ho通过抑制β相的阴极作用,增加自腐蚀电位,提高了合金的腐蚀性能。     

表面活性剂对镁合金基体上的非铬化镀镍涂层的腐蚀特性的作用

在镁合金AZ91D化学沉积了镍涂层,研究了非铬化预处理及表面活性物质对涂层腐蚀特性的影响。通过盐水试验(1mol/L HCl)和电化学极化试验(3.5%NaCl)检测了腐蚀性能。试验表明:化镀镍溶液中添加的表面活性剂可提高镁合金镍涂层上的抗腐蚀能力。此外,表面平整均匀的纳米和非晶相涂层提高了其抗腐蚀能力。极化试验表明,其腐蚀电位向正方转移,且腐蚀电流密度减低。浸泡试验和电化学极化试验都表明阳离子表面活化剂具有更好的提高抗腐蚀性能的作用。     

Y和Ce对AZ91D镁合金显微组织和力学性能的影响

为了开发低成本、高强度、耐高温的新型镁合金,研究了微量Y、Ce对AZ91D镁合金显微组织和力学性能的影响。研究结果表明:Y和Ce复合加入AZ91D镁合金,能明显细化组织晶粒,从而改善合金在室温和高温下的力学性能。当加入0.6%Ce-0.3%Y(质量分数)时,合金晶粒细化效果较好,其室温和高温力学性能比较理想。     

基于固体培养基(SCM)的镁合金的微生物腐蚀

采用固体培养基贴片法研究了镁合金的微生物腐蚀行为。利用扫描电镜(SEM)、极化曲线研究了AZ91镁合金在无菌和有硫酸盐还原菌体系中的腐蚀行为。通过形貌对比及电化学分析发现,硫酸盐还原菌加速了镁合金的腐蚀。细菌影响下的腐蚀形貌的主要特征是点蚀。细菌的代谢过程所导致的电极的阴极去极化加速了镁合金的点蚀的形成和发展。     

Initial corrosion behaviors of AZ91 magnesium alloy in the presence of SO2

The effects of SO2 on the initial atmospheric corrosion of AZ91D magnesium alloy were investigated in laboratory. Met-allographic observation, SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Proton Spectrograph) were used to analyze and discuss the initial surface morphology of corrosion layers and corrosion products. The corrosion rate of the alloy increases with increasing the content of SO2. The initial attack has the characteristics of localized corrosion and preferentially concentrates on a phase. MgO and Mg(OH)2 form at first, which provide a protective layer, then the existence of SO2 decreases the pH of the thin solution on the alloy, accelerates dissolution process, and promotes the formation of MgSO3·6H2O and MgSO4·6H2O, meanwhile cracks were found on the corrosion products with corrosion continuation. These soluble corrosion products and the cracks provide the paths for filtering oxygen and corrosion pollutants into the matrix, which results in severe localized co     

镁合金化学镀Ni-W-P合金

将AZ91D镁合金无铬处理后,以硫酸镍和钨酸钠为主盐,柠檬酸钠和碳酸钠为复合络合剂,在碱性镀液中通过调整镀液组成,得到W含量较高的Ni-W-P合金镀层。此镀层中W及P的质量分数分别为4.50%和4.84%。通过孔隙率和极化曲线测量了此镀层的耐蚀性能,表明该镀层能够很好地提高AZ91D镁合金的耐蚀性。     

Corrosion resistance of cerium conversion film electrodeposited on Mg-Gd-Y-Zr magnesium alloy

The cerium conversion film was applied to improving the corrosion resistance of Mg-Gd-Y-Zr magnesium alloy. The film was electrodeposited on the surface of the Mg-RE alloy in cerium nitrate solution. The compositions and morphologies were analyzed by X-ray diffraction(XRD), scanning election microscopy (SEM). The corrosion behaviors of the film were investigated electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests and immersion tests. The results show that the optimum parameters for electrochemical deposition are as follows: pH 10.0, time 30 min, 50 mmol/L Na₂CO₃ and temperature 25 °C by the designed experiments according to the orthogonal table L(9, 3⁴). The corrosion protection efficiency is dependent on the deposition parameters. The cerium conversion film shows better corrosion protection behavior than chromate conversion film on Mg-Gd-Y-Zr magnesium alloy. Foundation item: Project (5133001E) supported by the Major State Basic Research and Development Program of China     

硅烷膜固化方式对AZ91镁合金耐蚀性的影响

为了改善AZ91镁合金的耐蚀性,采用包括加热固化、碱液固化和微电水固化在内的3种不同固化方式制备了硅烷膜,并对其耐蚀性进行了研究.采用光学显微镜和扫描电子显微镜观察了试样的腐蚀形貌,并采用极化曲线分析了硅烷膜的耐蚀性.结果表明,经硅烷化处理后,AZ91镁合金表面可以形成一层硅烷膜,且很好地抑制了镁合金的腐蚀;对比3种不同固化方式后发现,碱液固化效果最佳,其次是加热固化,微电水固化效果虽不及前两者,但也有较好的效果.     

镁合金阳极氧化膜的微观结构与耐蚀性能研究

为了提高镁合金的耐蚀性能，采用扫描电镜(SEM)、电化学测试和盐雾试验等技术，对不同阳极氧化液中得到的镁合金AZ91D阳极氧化膜层的微观结构及其耐蚀性能进行了评价.所有工艺采用交流电源、氧化液无氟、铬和无磷，有利环境保护.先后对外加交流电压、Na2SiO3浓度、NaAlO2浓度，以及Na2SiO3和NaAlO2的协同作用对膜层腐蚀性能的影响规律进行了考察.结果表明，外加电压和氧化液组成对氧化膜的微观结构及其性能有着至关重要的影响.在碱性溶液中，NaAlO2和Na2SiO3的协同作用下，得到的阳极氧化膜的综合耐蚀性能优异，自腐蚀电流密度达到1.87×10-7A/cm2，耐中性盐雾大于500 h（氧化膜未封孔）.     

钕对AZ91镁合金组织及机械性能的影响

采用微观分析、机械性能测试及断口分析等方法研究了钕对AZ91-Nd镁合金(w(Nd)=0,0.1%,0.3%,0.5%,1.0%,1.5%)的微观组织和机械性能的影响。结果表明:Nd以固溶和金属间化合物(A l11Nd3)的形式存在时具有细化晶粒、抑制二次β相析出、使不完全离异共晶转化为离异共晶的作用;Nd通过固溶强化、析出强化和细晶强化增加了合金强度和硬度,并改善了塑性;加入Nd后合金的断裂机制从脆性解理断裂转变为准解理断裂。     

镁合金无铬前处理工艺及化学镀镍

以马日夫盐为主盐,乙醇为溶剂,在AZ91D镁合金上获得一层不完全的转化膜,避免了铬酸刻蚀和HF酸活化.然后以硫酸镍作为化学镀镍磷合金镀液的主盐,选择合适的络合剂,实现了在AZ91D镁合金的表面直接化学镀Ni-P合金,得到的镀层均匀致密,无明显缺陷.对镁合金化学镀镍基合金的无铬前处理工艺参数进行了探讨,并对前处理膜层和后...     

Corrosion protection of AM50 magnesium alloy by Nafion/DMSO organic coatings

The effectiveness of the corrosion protection of Nafion/Dimethysulfoxid （DMSO） organic coatings for AM50 magnesium alloy prepared by simple immersion and heat treatment was investigated. Its corrosion resistance and morphologies of the Nafion/DMSO organic coatings were studied by electrochemical corrosion testing and optical microscopy. The results show that Nafion/DMSO organic coatings can improve the corrosion resistance of AM50 magnesium alloy effectively. Also, the corrosion resistance increases with the surface density of the organic coatings.     

镁合金应力腐蚀开裂敏感性影响因素及防护措施

在腐蚀性环境中,镁合金具有十分强烈的应力腐蚀敏感性,往往降低材料性能,制约镁合金的应用.基于近些年来镁合金应力腐蚀开裂导致了一系列工业事故频繁发生的事实,需要了解和重视镁合金应力腐蚀开裂敏感性的影响因素及防护方法,针对影响镁合金应力腐蚀开裂敏感性的各项因素进行了综合的分析,并从应力,腐蚀环境,合金品质等方面对国内外镁合金应力腐蚀开裂防护措施的最新进展进行了介绍,并提出了镁合金应力腐蚀及防护领域未来所面临的任务.     

磷化液中ZnO对AZ61镁合金磷化膜的影响

探讨了锌系磷化液中主要的成膜物质ZnO的质量浓度对AZ61镁合金磷化膜的微观结构和性能的影响.利用金相显微镜、扫描电镜、能谱分析仪观察和分析了磷化膜的结构、表面形态和组成成分,并通过阳极极化曲线测量评价了磷化膜的耐腐蚀性能.结果表明:在低ZnO质量浓度的磷化液中,获得的磷化膜比较疏松且不完整,其并未表现出优异的耐腐蚀性;在高ZnO质量浓度的磷化液中,得到的磷化膜晶粒较粗大,厚度不均匀,耐腐蚀性不佳;在中等ZnO质量浓度2.0g／L的磷化液中,得到了均匀、完整的磷化膜层,极化曲线测量表明了其在质量分数为3.5％NaCl溶液中具有较好的耐腐蚀性.     

Effect of RE on the ignition-proof, microstructure and properties of AZ91D magnesium alloy

The magnesium alloy is prone to burn during die-casting, which limits its applications severely, so the effect of adding rare earth （RE） on the ignition-proof of AZ91D Mg alloy is studied. The results indicate that the addition of mischmetal RE elements has a remarkable influence on the ignition-proof property of the magnesium alloy. It is found that the ignition temperature of the magnesium alloy can be greatly raised by adding a proper amount of RE. When the amount is 0.1wt%, the ignition temperature reaches 877℃ which is 206℃ higher than that of AZ91D without RE and the mechanical properties of the alloy are also improved, However, the amount of RE must be properly controlled because too much RE would induce grain coarsening and reduce the mechanical properties.     

Plastic deformation behavior of ZK60 magnesium alloy with addition of neodymium

The hot deformation simulation of a ZK60 magnesiuln alloy at different temperatures from 373 to 673 K and different strain rates of 0.1, 0.01 and 0.002 s^-1 was studied by using the Gleebe-1500 simulator. The plastic deformation behavior was measured and the deformation activation energy was calculated. The microstructures of ZK60 magnesium alloy with an addition of neodymium during the deformation process were observed by using Polyvar-MET optical microscope and Tecnai G^2 20 TEM. The results show that the working hardening, the dynamic recovery and the dynamic recrystallization occur during the plastic deformation process at different temperatures and strain rates. The dynamic recrystallization starts when the temperature is over 473 K and the DRX grain size after hot deformation is only 5-10 μm. So the refined grains improve both the tensile strength and the elongation of alloys at room temperature. Neodymium is added into the alloy and a precipitate phase Mg12Nd that impedes the movement of dislocations is formed, which benefits to increasing mechanical properties of ZK60 magnesium alloy.