关键词： Micro-arc oxidation   2-aminobenzimidazole   Halloysite nanotube   Corrosion inhibitor  

摘要： Micro-Arc oxidation (MAO) coatings with actively protective functionality by incorporating 2-aminobenzimidazole (2-ABi) loaded halloysite nanotubes (HNTs) was presented. The coatings were characterized by SEM, EDX and XRD. Corrosion behavior was evaluated by EIS, PDP and salt spray test. With the SEM and EDX analysis, the existence of HNT or 2ABi-loaded HNT was confirmed. The OCP evolution, EIS complex spectra and the result of salt spray test showed the enhanced corrosion resistance of 2-ABi-HNT MAO coating owing to the self-healing effect, suggesting 2-ABi has good potential as corrosion inhibitor for Mg alloys.

关键词： Resolved shear stress   Deformation twinning   Transient X-ray diffraction   Magnesium alloys   Impact loading  

摘要： We investigate deformation twinning in a highly textured magnesium alloy plate of Mg-3.1%Al-0.9%Zn-0.4%Mn under edge-on impact with in situ, synchrotron-based, ultrafast X-ray diffraction measurements, and corresponding stress states are simulated with the finite element method. Deformation twinning and its anisotropy under the triaxial stress condition are explained by a statistical analysis of resolved shear stress. The critical resolved shear stress criterion is applicable under complicated stress conditions induced by high strain rate impact loading. Three typical simple stress conditions are further explored as verification and application cases: uniaxial-stress, uniaxial-strain, and plane-stress. Extension twinning in the magnesium alloy is prone to occur for impact loading applied perpendicular to the crystallographic c-axis, regardless of the exact stress conditions.

关键词： Crystal growth   Thin films   Corrosion   Metals and alloys  

摘要： The two oriented 2D nanocrystalline Zn-Al Layered Double Hydroxides films, with c-axis parallel (//) and perpendicular (perpendicular to) to the substrate, have been successfully prepared in situ by a facile hydrothermal crystallization method on the AZ91D magnesium alloy. The as-prepared films showed their uniform and compact structure. In the electrochemical test, the corrosion current density (i(corr)) of ZnAl-LDHs crystal film with c perpendicular to s in 0.1 M NaCl solution was decreased from 6.78 x 10(-4) A/cm(2) to 1.65 x 10(-7) A/cm(2), and the Rct in EIS was increased from 148.7 ***(2) to 4575 ***(2), while that of c//s were only 1.06 x 10(-5) A/cm(2) and 406.3 ***(2). This result demonstrated the c-axis perpendicular oriented ZnAl-LDHs crystal film greatly limited the penetration of aggressive ions into the underlying metal surface, effectively protecting the metal from corrosion. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Biodegradable magnesium alloy   Vertebral body stent   Damage evolution   Configurational forces   Stress corrosion  

摘要： Magnesium alloy has attracted most of the recent attention as a candidate for stent material due to their biocompatible and biodegradable nature. However, their corrosion behavior in the human body is still a major issue in research today. In this paper, a strategy to simulate damage evolution in biodegradable magnesium alloy stent is given by introducing a configurational damage model. In the framework of continuum thermodynamics, one can characterize the development and evolution of local damage of materials by establishing internal variables in phenomenological method. We believe that corrosion can damage alloy in two different ways: surface corrosion and stress corrosion. Surface corrosion is described using uniform damage, when the structure is exposed in a corrosion environment;Configurational force is used to describe stress corrosion when the structure is exposed in a stimulating environment. We then select global damage and radial resistance force to perform the changes of macroscopic mechanical properties during stent degradation. Finally, the well performance of the proposed model is demonstrated through several numerical examples. This model has the potential to assist stent design and development in the future. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Magnesium alloy   Laser surface texturing   Phosphate conversion coating   Corrosion resistance  

摘要： In this work, we proposed a surface modification strategy to improve corrosion resistance of magnesium alloy by combining laser surface texturing (LST) with phosphate conversion coating (PCC). The surface and section morphologies, adhesive performance and electrochemical corrosion properties of the coated samples were investigated. Results demonstrate that the multimodal surface roughness and high specific area generated by LST facilitate the deposition of coating, increase the adhesion of coating and reduce the shedding rate of coating in the scratch test. Electrochemical analyses reveal that the coated sample with LST pretreatment shows superior corrosion properties, and fewer areas were damaged by corrosive medium compared with the coated sample without LST. Immersion test results reveal that LTC sample shows the best long-term corrosion resistance among all *** underlying mechanisms of the PCC with LST pretreatment to improve the anticorrosive performance of Mg alloys are proposed. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Tribological Properties   Stir casting   Az91D magnesium alloy   Cerium oxide   Lanthanum oxide  

摘要： Purpose The aviation field requires a material with the ability to withstand severe environmental conditions. The purpose of this paper is to provide higher wear resistance and improve the lifetime of aircraft. Hence, it is vital to enhance the wear resistance and strength of the material. Design/methodology/approach In this investigation, the Az91D magnesium alloy was reinforced with lanthanum (La2O3) and cerium oxide (CeO2) nanoparticles by stir casting and heat treatment process and the tribological and mechanical properties were analyzed. Findings The results showed the Az91D/CeO2 composite exhibited higher density (1.96 g/cm3) and lower porosity (1.01%) compared to other materials due to the diffusion of CeO2 nanoparticles in between the atoms of Az91D alloy. The hardness of Az91D/ CeO2 & Az91D/ La2O3 was improved by 38% and 34%, respectively, compared to Az91D alloy owing to the reinforcing effect of hard nanoparticles. Further, the inclusion of nanoparticles decreased the mass loss and showed lower wear rate compared to the Az91D alloy due to the pinning effect of nanoparticles. In addition, the friction coefficient was observed in the order of Az91D > Az91D/ La2O3 > Az91D/ CeO2. Moreover, the heat treatment displayed positive results on the properties of all the materials. Originality/value This work is original as the combination of cerium oxide nanoparticles with Az91D magnesium alloy is not tried by earlier investigators. Further, the comparative performance of both lanthanum and cerium oxide nanoparticles on the tribological and mechanical behavior of Az91D alloy has been analyzed for aviation application. This study will provide new information to the scientific world to increase the lifetime of aviation structures.

关键词： Mg-4Al-2Sn含锡镁合金   挤锻复合成形   显微组织   力学性能  

摘要： 采用不同的挤压温度和锻压温度对新型含锡镁合金Mg-4Al-2Sn试样进行了挤锻复合成形试验,并进行了显微组织和力学性能的测试、对比和分析。结果表明:随挤压温度和锻压温度的升高,试样的晶粒先细化后粗化,抗拉强度、屈服强度先增大后减小,组织改善。在350℃挤压然后380℃锻压的试样抗拉强度、屈服强度最大,分别为325、230 MPa。

关键词： 碳化钛   镁合金   阳极氧化   耐腐蚀性  

摘要： 以纳米碳化钛(TiC)为添加剂,研究其对镁合金阳极氧化过程的作用机制,通过扫描电子显微镜、X射线衍射试验、塔菲尔腐蚀试验等表征氧化膜的形貌结构与性能。结果表明:添加纳米碳化钛能有效改善镁合金的阳极氧化过程,提升镁合金氧化膜的耐腐蚀性能;当添加3~4 g·L^(-1)纳米碳化钛时,获得的氧化膜性能最佳。

关键词： 镁合金   固溶处理   组织   力学性能   腐蚀  

摘要： 研究了Mg-0.5Zr-1.8Zn-x Gd (x=0,0.5,1.0,1.5,2.0,2.5,质量分数,%)镁合金经过470℃和10 h固溶处理后的组织、力学性能和耐腐蚀性能。结果表明,Gd含量在0%-2.5%范围内,随着Gd含量增加,合金晶粒尺寸逐渐减小。当Gd含量低于1.5%时,合金元素几乎完全固溶于合金基体中,第二相主要由纳米尺度的(Mg,Zn)3Gd析出颗粒组成。当Gd含量在1.5%-2.5%范围时,合金中出现未固溶的微米尺度的(Mg,Zn)3Gd相,并且该相数量和尺寸随着Gd含量增加而增加。由于组织均匀分布和纳米尺寸的第二相颗粒存在,Mg-0.5Zr-1.8Zn-1.5Gd合金具有优异的力学性能和耐腐蚀性能。在120 h浸泡实验中,Mg-0.5Zr-1.8Zn-1.5Gd合金平均腐蚀速率首先降低,然后增加,接着缓慢降低,最后,随着浸泡时间延长,腐蚀速率最终变得稳定。

关键词： 搅拌摩擦加工   AZ61镁合金   加工方向   组织演变   力学性能  

摘要： 采用搅拌摩擦加工技术(Friction stir processing,FSP)对轧制态AZ61镁合金进行单道次加工,利用EBSD和SEM/EDS及室温拉伸、显微硬度测试等表征手段,研究了加工方向对加工区域微观组织演变及其对力学性能的影响规律.结果表明:沿轧制方向(Rolling direction,RD)和横向(Transverse direction,TD)FSP制备的镁合金晶粒尺寸分别为3.5μm和4.3μm,基面施密特因子平均值分别为0.42和0.34;沿RD方向制备的镁合金中第二相呈细小弥散分布,而TD方向的第二相颗粒较为粗大;两个方向制备的镁合金抗拉强度相当,沿RD和TD方向制备的镁合金的屈服强度分别为90 MPa和104 MPa、伸长率分别为34.8%和28.6%,而RD方向制备的镁合金硬度高于TD方向.屈服强度与霍尔佩奇关系不符,受织构影响,而硬度分布符合霍尔佩奇关系.