AZ31镁合金磁控溅射镀铝膜的性能研究

采用超真空磁控溅射镀膜设备在AZ31镁合金表面进行了铝保护膜的镀覆,利用辉光放电光谱分析和纳米压痕/划痕试验技术,研究了镀层的成分和显微力学性能随薄膜深度的分布。结果表明,铝镀层在镁合金基体表面形成,镀层和基体之间存在混融的过渡层,铝镀层的表面硬度、弹性模量等高于镁合金基体的,并随深度增加而递减,膜层与基体结合良好并表现出一定塑性,镀铝膜有利于镁合金表面防护层的形成。     

Enhanced corrosion performance of magnesium phosphate conversion coating on AZ31 magnesium alloy

Magnesium phosphate conversion coating (MPCC) was fabricated on AZ31 magnesium alloy for corrosion protection by immersion treatment in a simple MPCC solution containing Mg²⁺ and PO^3?₄ ions. The MPCC on AZ31 Mg alloy showed micro-cracks structure and a uniform thickness with the thickness of about 2.5 µm after 20 min of phosphating treatment. The composition analyzed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that the coating consisted of magnesium phosphate and magnesium hydroxide/oxide compounds. The MPCC showed a significant protective effect on AZ31 Mg alloy. The corrosion current of MPCC was reduced to about 3% of that of the uncoated surface and the time for the deterioration process during immersion in 0.5 mol/L NaCl solution improved from about 10 min to about 24 h.     

磁控溅射和等离子体电解氧化双重工艺处理AZ31镁合金的耐蚀和耐磨性能

为了提高AZ31镁合金的耐磨和耐腐蚀性能,通过磁控溅射法在合金表面涂覆约11μm的纯铝层,然后分别在铝酸盐和硅酸盐电解液中通过等离子电解氧化(PEO)进行表面处理.涂层的性能通过干滑动摩擦试验和电化学腐蚀试验进行研究.铝酸盐涂层在10和20 N的负载下均表现出良好的耐磨性能;硅酸盐涂层只在较低的载荷下(10 N)表现出...     

AZ31镁合金表面液相渗铝的工艺与性能

采用液相扩渗技术在挤压态AZ31镁合金表面快速渗入铝，在合金表面获得过共晶渗层，并对渗层的成分、相组成、扩渗过程、纳米硬度和腐蚀性能进行分析。结果表明：AZ31镁合金在480℃热扩渗铝过程中发生了“熔化—凝固”变化，渗层为典型的过共晶组织：渗铝层含有Mg17A112相和镁的铝饱和固溶体，这种渗层具有较高的纳米硬度和较好的耐腐蚀性能；通过提高扩渗温度进行液相扩渗可以大大提高扩渗速度，但由于快速凝固收缩会造成表层产生起伏现象，控制冷却速度可以将表层起伏控制在可接受的范围。     

Comparison in characterization of composite and sol-gel coating on AZ31 magnesium alloy

An Al2O3 protective coating on magnesium alloy AZ31 was prepared by a repeated direct sol-gel process annealing at 300℃and a composite coating was also deposited using Al2O3 particles dispersed sol followed by phosphating treatment and annealing at 300℃.The morphologies,structures and critical adhesive loads as well as corrosion properties of the coatings were comparatively investigated by scanning electron microscopy(SEM),X-ray diffractometry(XRD),nanoscratch test and electrochemical measurement.The results show that the composite coating has a more uniform,crack-free layer and improved adhesion to the substrate as compared with that of the repeated direct sol-gel coating owing to its lower heat strain.The main phases in both coatings consist ofγ-Al2O3 andδ-Al2O3 derived from annealed alumina sol,and the composite coating has an anticorrosion performance which is superior to that of the repeated direct sol-gel coating.     

AZ31镁合金钕基转化膜研究

通过化学转化成膜在AZ31镁合金表面制备了钕基转化膜。利用称重实验和OCP测试研究了钕基转化膜的成膜过程,利用SEM,EDS和XPS分别研究了膜层形貌,微观结构和组成成分。研究了空白样品与镀膜样品在3.5 wt.% NaCl 溶液中浸泡不同时间后样品表面形貌和成分,结果表明钕基转化膜可以有效的降低AZ31镁合金在NaCl溶液中的腐蚀速率。利用XRD和电化学测试研究了经过后处理以后的钕基转化膜的成分和耐蚀性能,结果说明后处理可以进一步改善钕基转化膜的腐蚀性能。     

Microstructure and properties of oxalate conversion coating on AZ91D magnesium alloy

The oxalate coating formed on AZ91D magnesium alloy by chemical conversion treatment methods in oxalate salt solutions was investigated. The surface morphologies and chemical composition of coating were examined using scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-ray (EDX). Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and salt spray tests were employed to evaluate corrosion protection of the coating to substrate in 5% NaCl solution. The mechanism of coating formations was also considered in details. The results indicate that a compact and dense surface morphology with fine particle clusters of the oxalate coating on magnesium alloy is presented, which mainly consists of oxide or/and organic of Mg, Al and Zn. And the anti-corrosion of the magnesium after oxalate conversion treatment is better than that of the magnesium substrate. The results of salt spray test for oxalate coating is evaluated as Grade 9 according to ASTM B117. The electric resistance of oxalate chemical conversion coating to substrate is below 0.1 Ω.     

Influence of intermetallic Al-Mn particles on in-situ steam Mg-Al-LDH coating on AZ31 magnesium alloy

The influence of intermetallic Al-Mn particles on the corrosion behavior of in-situ formed Mg-Al layered double hydroxide (Mg-Al-CO₃^2--LDH) steam coating on AZ31 Mg alloy was investigated. The alloy was pretreated with H₃PO₄, HCl, HNO₃ or citric acid (CA), followed by hydrothermal treatment, for the fabrication of Mg-Al-LDH coating. The microstructure, composition and corrosion resistance of the coated samples were investigated. The results showed that the surface area fraction of Al-Mn phase exposed on the surface of the alloy was significantly increased after CA pretreatment, which promotes the growth of the Mg-Al-LDH steam coating. Further, the LDH-coated alloy pretreated with CA possessed the most compact surface and the maximum coating thickness among all the coatings. The corrosion current density of the coated alloy was decreased by three orders of magnitude as compared to that of the bare alloy.     

Environmentally friendly anodization on AZ31 magnesium alloy

A novel anodization which is environmentally friendly,low voltage and low energy consumption was developed to improve corrosion resistance of AZ31 magnesium alloy.The corrosion resistance of the anodic films was studied by electrochemical impcdance spectroscopy(EIS) and potentiodynamic polarization techniques.The microstructure and compositions of films were examined by SEM,XPS and XRD.A new kind of organic additive used in the electrolyte is friendly to the environment.The compact, intact and uniform co...     

Preparation of Ni-Cu-Mo-Cr film deposited on AZ31magnesium alloy by double glow sputtering with Cu interlayer

For improving the corrosion resistance of AZ31magnesium alloy, a double glow sputtering deposited Ni-Cu-Mo-Cr film with brush plating Cu interlayer is applied to deposit a metal amorphous/nanocrystal film on AZ31magnesium alloy. Using a brush plated Cu interlayer, the content of noble elements, such as Ni, Cr, and Mo, is higher than that of a Ni-based film without Cu interlayer. The microstructure of the Ni-Cu-Mo-Cr alloy film with the brush plated Cu interlayer confirms that the film is classified into two regions, i.e., an amorphous layer on the outmost surface and an underlying nanocrystalline layer with a grain size of less than 5 nm. The Ni-based alloy amorphous film formed on AZ31magnesium alloy was investigated using an electrochemical polarization measurement. Compared with the AZ31 magnesium alloy, the sputter-deposited Ni-based alloy film and the sputter-depostion Ni-based alloy film with a brush plated Cu interlayer formed on AZ31 magnesium alloy exhibit obvious passivation phenomena.     

Organic-magnesium complex conversion coating on AZ91D magnesium alloy

An organic-magnesium complex conversion (OMCC) coating on AZ91D magnesium alloy was obtained by treating in a solution containing organic compounds. SEM, FESEM and XPS were used to examine the surface morphology, thickness and structure of the conversion coatings. The results show that the continuous and uniform conversion coating is deposited on AZ91D alloy and the main component of the coatings is organic compound containing benzene ring, which forms a chemical bond with magnesium. The polarization measurement and salt spray test show that the corrosion resistance of the conversion coating is much higher than that of traditional chromate conversion coating.     

Preparation and characterization of Ca-P coating on AZ31 magnesium alloy

A Ca-P coating consisting of biodegradableβ-tricalcium phosphate[β-TCP,β-Ca3(PO4)2]accepted for medical application was coated on a biodegradable AZ31 alloy by chemical deposition to improve the corrosion resistance.The good bonding strength of the coating is obtained.The results show that the corrosion potential of the Ca-P coated AZ31 alloy increases significantly,and MG63 cells show good adherence,proliferation and differentiation on the surface of the coated alloy.The Ca-P coating might be an effective way to improve the surface bioactivity of magnesium alloys.     

Fabrication and properties of the superhydrophobic ceria-based composite coating on magnesium alloy

A superhydrophobic ceria-based composite coating is developed to improve anticorrosion properties of AZ61 magnesium alloy, fabricating via chemical conversion method followed by hydrothermal treatment. The cerium conversion coating has a block structure with microcracks. After the hydrothermal treatment, a dense CeO₂ layer, porous CeO₂ nanorods, and stearic absorbing layers are grown stepwise on the conversion coating. And the composite coating is hydrophobic or even superhydrophobic and has almost no microcracks. As the hydrothermal reaction time increases, the water contact angle of the composite coating first increases and then decreases, and it reaches the maximum value of 152° after hydrothermal treatment for 4 h. Both the dense CeO₂ layer and the superhydrophobic stearic absorbing layer can effectively prevent the electrolyte from contacting the substrate; the corrosion current density of the superhydrophobic composite coating is lower than that of the hydrophilic composite coating and the cerium conversion coating, and has the best corrosion resistance.     

Barium phosphate conversion coating on die-cast AZ91D magnesium alloy

Poor corrosion resistance limits the application of magnesium alloys.Conversion coating is widely used to protect magnesium alloys because of easy operation and low cost.A novel conversion coating on die-cast AZ91D magnesium alloy containing barium salts was studied.The optimum concentrations of Ba(NO_3)_2,Mn(NO_3)_2 and NH_4H_2PO_4 are 25 g/L,15 mL/L and 20 g/L,respectively,based on orthogonal test results.The treating time,solution temperature and pH value are settled to be 5-30 min, 50-70℃and 2.35-3.0...     

AZ31镁合金表面碳钠铝石转化膜的性能(英文)

开发一种环境友好的方法合成碳钠铝石转化膜以提高AZ31镁合金的耐蚀性。该膜由两步法制得:首先将AZ31合金浸泡在一直通CO2气体的Al2(SO4)3溶液中,获得前躯体膜;随后将该前躯体膜浸泡在溶有Al的Na2CO3溶液中以获得碳钠铝石膜。通过环境扫描电镜观察转化膜的表面形貌,并利用EDS能谱和X射线衍射分析其化学成分。采用电化学和浸泡实验来评价该转化膜对AZ31合金的防护作用。结果表明:膜的表面存在网状裂痕,其成分主要为碳钠铝石NaAlCO3(OH)2、Al(OH)3和Al5(OH)13(CO3)·5H2O。该膜能提高Mg基体的自腐蚀电位,并减少其腐蚀电流密度。浸泡实验后,除了局部小区域有个别点蚀坑外,膜基本保持完整;而基体却腐蚀严重。说明碳钠铝石转化膜能很好地保护镁合金。     

Preparation and corrosion resistance of superhydrophobic coatings on AZ31 magnesium alloy

In order to improve the corrosion resistance of the Mg alloys, the superhydrophobic coatings on AZ31 Mg alloy were prepared by a two-step process of micro-arc oxidation treatment and superhydrophobic treatment in stearic acid ethanol solution. The effects of voltages, frequencies and treatment time on the contact angle of the superhydrophobic treated sample were investigated. The results showed that with increasing the voltage, frequency and treatment time, all of the contact angles of the superhydrophobic treated sample increased first, and then decreased, reaching the maximum values at 350 V, 1000 Hz and 5 min, respectively. The optimal superhydrophobic coating was mainly composed of MgO and Mg₂SiO₄ phases, with the pore diameter of ～900 nm, the thickness of ～6.86 μm and the contact angle of 156.96°. The corrosion current density of the superhydrophobic AZ31 sample decreased by three orders of magnitude, and the amount of hydrogen evolution decreased by 94.77% compared with that of the AZ31 substrate sample.     

A novel dual nickel coating on AZ91D magnesium alloy

Magnesium alloys covered with metal coating display excellent corrosion resistance,wear resistance,conductivity and electromagnetic shielding properties.The electroless plating Ni-P as bottom layer following the electroplating nickel as surface layer on AZ91D magnesium alloy was investigated.The coating surface morphology was observed with SEM and the structure was analyzed with XRD.Electrochemical tests and salt spray tests were carried out to study the corrosion resistance.The experimental results indi...     

机械研磨对AZ31镁合金化学镀镍磷镀层性能的影响

在AZ31镁合金化学镀镍磷的过程中施加机械研磨作用,获得了具有新特性的镍磷镀层。扫描电镜观察表明,施加机械研磨获得的镍磷镀层的晶粒细化、致密性提高、消除了镀层中的孔隙。镀层截面的形貌结果显示,与传统化学镀镍磷层相比,施加机械研磨后镀层与基体的结合处形成了一个合金化的过渡区域,使镀层与基体的结合力得到显著的提高。由动电位极化曲线测试结果可知,施加机械研磨后镀层的自腐蚀电位提高到-0.2 V,相对传统化学镀镍磷层的电位提高了0.9 V,耐蚀性能显著提高。     

Wear resistance of ceramic coating on AZ91 magnesium alloy by micro-arc oxidation

The ceramic coating formed on AZ91 magnesium alloy by micro-arc oxidation （MAO） was characterized. The results show that the ceramic coating （3.4-23 μm in thickness）on the surface ofAZ91 alloy was attained under different micro-arc oxidation treatment conditions, which consist mainly of MgO, Mg2SiO4 and MgSiO3 phases. Nano-hardness in a cross-sectional specimen was determined by nano-indentation experiment. The MAO coatings exhibit higher hardness than the substrate. Dry sliding wear tests for the MAO coatings and AZ91 alloy were also carded out using an oscillating friction and wear tester in a ball-on-disc contact configuration. The wear resistance of the MAO coatings is improved respectively under different treatment time as a result of different structures of ceramic coatings formed on AZ91 alloy.