混合稀土对AZ91镁合金在NaCl溶液中的腐蚀行为影响

通过静态失重法、极化曲线和交流阻抗测试研究了混合稀土 (Re)对AZ91镁合金腐蚀行为的影响。结果表明 :Re的加入使AZ91微观组织得到改善 ,减缓了AZ91镁合金在NaCl溶液中的腐蚀     

混合稀土对AZ91镁合金在NaCl溶解中的腐蚀行为影响

通过静态失重法，极化曲线和交流阻抗测试研究了混合稀土（Re)对AZ91镁合金腐蚀行为的影响。结果表明：Re的加入使AZ91微观组织得到改善，减缓了AZ91镁合金在NaCl溶液中的腐蚀。     

镁合金健身器材的表面转化膜制备与性能研究

采用正交试验法对AZ91镁合金表面(La+Ce)双稀土转化膜进行了磷酸盐致密化工艺优化,并对比分析了基材和稀土转化膜致密化前后的耐腐蚀性能。结果表明,致密化工艺参数中对转化膜耐腐蚀性能的影响从大至小的顺序为:致密化温度致密化时间(NH_4)_3PO_4浓度,正交极差分析结果优化得到的AZ91镁合金的最佳稀土转化膜致密化工艺为致密化温度45℃、致密化时为3min和(NH_4)_3PO_4浓度6%;磷酸盐致密化处理后可在稀土转化膜表面形成CePO_4、Mg_3(PO_4)_2和LaPO_4相,并对致密化处理前的(La+Ce)双稀土转化膜表面的裂纹/孔洞缺陷进行填补和修复;析氢腐蚀、电化学阻抗谱和极化曲线测试结果相吻合,即3种试样的耐腐蚀性能从高至低顺序为:致密化后的试样致密化前的试样空白试样,即(La+Ce)双稀土转化膜可以对AZ91镁合金起到保护作用,且经过磷酸盐致密化处理后试样的耐腐蚀性能会进一步提高。     

稀土对AZ91镁合金阻燃性和机械性能的影响

针对应用最广的镁铝锌锰系镁合金AZ91,探讨了La的加入对其阻燃性和机械性能的影响.在自制覆盖剂保护下,按照AZ91镁合金化学计量比备料,熔铸了3种不同稀土含量(0,0.2%,0.4%)的样品.对样品进行燃点、硬度测定和金相观察.结果表明,富La稀土不仅可有效地提高镁合金的燃点(在AZ91系镁合金中添加0.4%的富镧稀土可使燃点提高15℃),还可细化晶粒,显著提高了镁合金的硬度,合金的布氏硬度由不含稀土时的548.8 MPa提高到656.6 MPa.     

镁合金健身器材的表面转化膜制备与性能研究北大核心CSCD

采用正交试验法对AZ91镁合金表面(La+Ce)双稀土转化膜进行了磷酸盐致密化工艺优化,并对比分析了基材和稀土转化膜致密化前后的耐腐蚀性能。结果表明,致密化工艺参数中对转化膜耐腐蚀性能的影响从大至小的顺序为:致密化温度>致密化时间>(NH4)3PO4浓度,正交极差分析结果优化得到的AZ91镁合金的最佳稀土转化膜致密化工艺为致密化温度45℃、致密化时为3min和(NH4)3PO4浓度6%;磷酸盐致密化处理后可在稀土转化膜表面形成CePO4、Mg3(PO4)2和LaPO4相,并对致密化处理前的(La+Ce)双稀土转化膜表面的裂纹/孔洞缺陷进行填补和修复;析氢腐蚀、电化学阻抗谱和极化曲线测试结果相吻合,即3种试样的耐腐蚀性能从高至低顺序为:致密化后的试样>致密化前的试样>空白试样,即(La+Ce)双稀土转化膜可以对AZ91镁合金起到保护作用,且经过磷酸盐致密化处理后试样的耐腐蚀性能会进一步提高。     

稀土元素（La，Ce）对镁合金电偶腐蚀的影响

针对镁合金化学和电化学活性较高，与其他金属材料接触时易产生电偶腐蚀的特点，主要研究了其电偶腐蚀特性及环境因素的影响规律。采用电化学方法通过测定电偶电流密度，研究了添加约1％混合稀土RE（45％La，50％Ce）的AZ91合金在NaCl溶液中与A3钢、紫铜偶接时的电偶腐蚀行为，探讨了溶液中氯离子浓度、偶接金属种类以及阴阳极面积比对电偶电流密度Jg^Mg的影响。结果表明：Cl^-浓度增大，Jg^Mg变大；阴阳极面积比越大，Jg^Mg也越大；偶接金属A3钢比紫铜更易促进镁合金的腐蚀；稀土La，Ce的添加使电偶腐蚀有效距离变窄。     

AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为

镁合金大气腐蚀的研究十分重要,而目前有关侵蚀性离子HCO_3~-在薄液膜下对镁合金腐蚀行为的研究报道较少。通过阴极极化曲线和电化学阻抗谱研究了AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为,详细讨论了液膜厚度、NaHCO_3浓度和时间等参数的影响,并用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)进行了表征。结果表明:随着液膜厚度的降低,阴极和阳极过程均受到限制,AZ91D镁合金腐蚀速率变小;NaHCO_3浓度增加会加剧AZ91D在薄液膜下的腐蚀;浸泡24.0 h后,本体溶液中腐蚀表现为均匀腐蚀,主要腐蚀产物为MgCO_3和Al_2O_3,而薄液膜下则表现为局部腐蚀,主要腐蚀产物为MgCO_3,Al_2O_3,MgCO_3·2H_2O和Mg_5(CO_3)_4(OH)_2·5H_2O。     

触变成形AZ91D镁合金在NaCl溶液中腐蚀行为的电化学分析

用动电位极化曲线和电化学阻抗谱的方法对触变成形AZ91D镁合金在NaCl水溶液中腐蚀行为进行了研究.结果表明:在相同浓度的NaCl水溶液中,随着腐蚀时间的延长,开路电位逐渐提高(正移),同一腐蚀电位下触变成形AZ91 D镁合金的阳极极化电流明显减小,电化学阻抗谱(EIS)显示其容抗减小,腐蚀产物在合金表面沉积,对基体金属具有一定的保护作用,因而其腐蚀速度减小;随着溶液中Cl-浓度的增大,开路电位呈下降(负移)趋势,且其开路电位的正移速度较慢,同一腐蚀电位下触变成形AZ91D镁合金的阳极极化电流增大,EIS显示其线性阻抗减小,腐蚀反应的过程加快,所以腐蚀速度增大.     

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.     

Corrosion properties and corrosion evolution of as-cast AZ91 alloy with rare earth yttrium

The corrosion resistance property and the corrosion evolution of as-cast AZ91 alloy with rare earth Y addition are investigated by using immersion tests, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The results show that the proper amount of Y in the alloys can improve the corrosion resistance of AZ91 alloys effectively. With the increment of Y, the corrosion rate of the modified AZ91 alloys by Y addition was markedly less than that of AZ91 alloy. The corrosion rate of AZ91 alloy with 0.3 wt.% Y was the slightest, but further addition of Y content over 0.3 wt.% make the corrosion heavier. The XPS analysis suggests that the compound film of AZ91 alloy with 0.3 wt.% Y is mainly composed of Mg(OH)₂ and MgCO₃ without any Al(OH)₃ and Al₂O₃, in addition, Y₂O₃ phase is found in the compound film of AZ91 alloy with 0.3 wt.% Y, which benefits to stabilize the surface film.     

Bio-corrosion characterization of Mg–Zn–X (X = Ca, Mn, Si) alloys for biomedical applications

The successful applications of magnesium-based alloys as biodegradable orthopedic implants are mainly inhibited due to their high degradation rates in physiological environment. This study examines the bio-corrosion behaviour of Mg–2Zn–0.2X (X = Ca, Mn, Si) alloys in Ringer’s physiological solution that simulates bodily fluids, and compares it with that of AZ91 magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed a better corrosion behaviour of AZ91 alloy with respect to Mg–2Zn–0.2Ca and Mg–2Zn–0.2Si alloys. On the contrary, enhanced corrosion resistance was observed for Mg–2Zn–0.2Mn alloy compared to the AZ91 one: Mg–2Zn–0.2Mn alloy exhibited a four-fold increase in the polarization resistance than AZ91 alloy after 168 h exposure to the Ringer’s physiological solution. The improved corrosion behaviour of the Mg–2Zn–0.2Mn alloy with respect to the AZ91 one can be ascribed to enhanced protective properties of the Mg(OH)₂ surface layer. The present study suggests the Mg–2Zn–0.2Mn alloy as a promising candidate for its applications in degradable orthopedic implants, and is worthwhile to further investigate the in vivo corrosion behaviour as well as assessed the mechanical properties of this alloy.     

Corrosion protection of biodegradable magnesium implants using anodization

Magnesium (Mg) and its alloys are emerging as a possible biodegradable implant material. However, Mg implants may degrade too quickly in the body, before the natural healing process is complete. In this work, anodization was investigated to slow down the initial corrosion of Mg in a simulated body corrosive environment. Pure Mg and AZ91D alloy were anodized and their corrosion resistance was compared in terms of anodization behavior and parameters such as applied voltage and current with different anodization time. Electrochemical impedance spectroscopy, DC polarization, and immersion testing were used to evaluate the corrosion resistance of Mg samples and further optimize anodization parameters. The results showed that anodization increased the corrosion resistance of both pure Mg and AZ91D samples. Further characterization showed the anodized layers on both pure Mg and AZ91D consisted of Mg, O and Si, in the mixture of MgO and Mg₂SiO₄.     

Effect of D-fructose on the in-vitro corrosion behavior of AZ31 magnesium alloy in simulated body fluid

The effect of addingd-fructose to simulated body fluid(SBF) on the corrosion behavior of AZ31 magnesium(Mg) alloy at 37.C and at a pH of 7.4 was studied by potentiodynamic polarization(PDP), electrochemical impedance spectroscopy(EIS), potentiostatic polarization and hydrogen(H2) collecting techniques,Raman spectroscopy technique, scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), X-ray photoelectron spectroscopy analysis(XPS) and Fourier transformed infrared(FTIR). The results demonstrated that the addition of fructose enhanced the deposition of phosphates forming thick and compact corrosion products, which inhibited the transmission of aggressive ions into the Mg substrate. As a result, both the anodic dissolution of Mg and negative difference effect(NDE) were suppressed. Thus, the corrosion resistance of AZ31 Mgalloy in SBF was significantly improved.     

不同表面处理工艺压铸镁合金涂层耐蚀性研究

为了研究不同表面处理工艺下压铸镁合金涂层的抗腐蚀性能,通过浸泡腐蚀和电化学腐蚀的方法,比较了微弧氧化和无铬化学氧化等表面处理试样的耐蚀性.结果表明,无铬化学氧化和微弧氧化处理能显著提高镁合金表面耐蚀性,而以微弧氧化处理更优;且两种处理方法覆盖层对孔洞、裂纹不敏感.根据交流阻抗图谱,拟合得到了微弧氧化、无铬化学氧化和未处理三种试样电化学腐蚀时体系的等效电路,拟合结果与实测结果吻合.XRD分析表明这两种处理方法得到的覆盖层中主体相均为Mg3Al2Si3O12等含硅的尖晶石型氧化物和Mg0.36Al2.44O4、MgAl2O4等不含硅的镁、铝复合氧化物,有利于提高镁合金耐蚀性.     

In-situ hydrothermal crystallization Mg(OH)2 films on magnesium alloy AZ91 and their corrosion resistance properties

Mg(OH)₂ films have been fabricated on magnesium alloy AZ91 substrates by an in-situ hydrothermal method. AZ91 alloy substrates act as both the source of Mg²⁺ ion and the support for the Mg(OH)₂ film in synthetic process. The effect of pH value and hydrothermal treatment time on the morphologies and corrosion resisting properties of Mg(OH)₂ film is studied. The obtained Mg(OH)₂ films are uniform and compact. The adhesion between the films and the substrate is strong due to the in-situ growth process, which enhances their potential for practical applications. Potentiodynamic polarization measurements showed that the Mg(OH)₂ films obtained at pH 10, 3 h exhibits the highest increase in corrosion potential at −0.7097 V and lowest i_corr, which suggests that it is the best effective film in improving the corrosion resistance of AZ91in all obtained films.     

Corrosion resistance of in-situ growth of nano-sized Mg(OH)2 on micro-arc oxidized magnesium alloy AZ31—Influence of EDTA

One of the major obstacles for the clinical use of biodegradable magnesium (Mg)-based materials is their high corrosion rate. Micro-arc oxidation (MAO) coatings on Mg alloys provide mild corrosion protection owing to their porous structure. Hence, in this study a dense Mg(OH)₂ film was fabricated on MAO-coated Mg alloy AZ31 in an alkaline electrolyte containing ethylenediamine tetraacetic acid disodium (EDTA-2Na) to reinforce the protection. Surface morphology, chemical composition and growth process of the MAO/Mg(OH)₂ hybrid coating were examined using field-emission scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectrophotometer. Corrosion resistance of the coatings was evaluated via potentiodynamic polarization curves and hydrogen evolution tests. Results manifested that the Mg(OH)₂ coating possesses a porous nano-sized structure and completely seals the micro-pores and micro-cracks of the MAO coating. The intermetallic compound of AlMn phase in the substrate plays a key role in the growth of Mg(OH)₂ film. The current density of Mg(OH)₂-MAO composite coating decreases three orders of magnitude in comparison with that of bare substrate, indicating excellent corrosion resistance. The Mg(OH)₂-MAO composite coating is beneficial to the formation of calcium phosphate corrosion products on the surface of Mg alloy AZ31, demonstrating a great promise for orthopaedic applications.     

Nd对AZ91镁合金显微组织和耐腐蚀性能的影响

用金相显微镜、扫描电镜和静态质量损失法对AZ91-xNd镁合金(x=1.1%,1.4%,1.9%)的微观组织和腐蚀性能进行表征,研究了Nd对AZ9l镁合金显微组织和耐腐蚀性能的影响.结果表明:稀土Nd的添加明显细化了合金的组织,使半连续网状β(Mgl7Al12)相变为细小的长条状,且分布更加均匀.在合金中还生成了颗粒状...     

Effect of glycine addition on the in-vitro corrosion behavior of AZ31 magnesium alloy in Hank's solution

This study reports on the effect of the addition of Glycine to Hank's solution on the in-vitro corrosion behavior of AZ31 magnesium (Mg) alloy at 37 ℃ and a pH of 7.4 studied by using potentiodynamic polarization (PDP),hydrogen collecting techniques and electrochemical impedance spectroscopy (EIS) in combination with surface characterization techniques such as optical microscopy (OM),scanning electron microscopy(SEM),energy dispersive spectroscopy (EDS),X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis (XPS).The results reveal that adsorption of glycine initially subdues the dissolution ofAZ31 Mg alloy while in long run it enhances the dissolution of the alloy due to the commencement of the chelation effect ofglycine with Ca2+ released from hydroxyapatite.The chelation ofglycine with Ca2+induces the formation of cracks in the surface film which further promotes the dissolution ofAZ31 Mg alloy thereby forming a porous corrosion products layer on the surface of the alloy.As a result,both the continuous dissolution of AZ31 magnesium alloy and the hydrogen evolution rate (HER) are enhanced with increasing the immersion time in Hank's solution.