Electroless plating of silver on AZ31 magnesium alloy substrate

Electroless plating of silver on AZ31 magnesium alloys via electroless plating and organic coatings (organosilicon heat-resisting varnish), was studied. The organic coating was made by immersing the samples into organosilicon heat-resisting varnish. The applicability of this method was verified by a subsequent metallization process. In this method the organic coating acted as interlayer between the substrate and silver film. When the reaction started, silver would deposit virtually onto the interlayer surface. X-ray diffraction and SEM analysis were used to investigate the morphology of the interlayer and silver film. The silver film has a rather perfect crystal structure. And the result of the cross-cut test indicates the adhesion between the substrate and interlayer is good enough. The potentiodynamic polarization curves for corrosion studies of the coated magnesium alloys were performed in a corrosive environment of 3.5 wt.% NaCl at neutral pH (7). The result reveals: comparing with the substrate, the corrosion resistance of the coated AZ31 magnesium alloys increases distinctly. Moreover, the silver coating has perfectly antibacterial and decorative properties. The method proposed in this work is environmentally friendly: non-toxic chemicals are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

还原剂对AZ31B镁合金表面化学镀Ni-B合金性能的影响

试验研究了还原剂浓度对镁合金表面化学镀Ni-B合金性能的影响.结果表明,还原剂浓度对化学镀Ni-B合金的镀速、成分、形貌、耐腐蚀性有很大的影响,当还原剂浓度为1.2mL/L时,镀速较大,而且镀层均匀、紧凑、细密,耐腐蚀性良好.     

Extrusion process and property of AZ31 magnesium alloy

The microstructure and mechanical properties of extruded AZ31 magnesium at different extrusion temperature were investigated.The results show that,at 380 ℃,when the extrusion ratio is 23,the AZ31 magnesium alloy has a dense recrystallized microstructure and good mechanical properties.On one hand,if the extrusion ratio is too small,grain crushing effect is not obvious,and part of the grain is not dynamic recrystallization.On the other hand,larger extrusion ratio can lead to grain growth and banded structure.Tensile fracture characteristics of extruded AZ31 magnesium alloy is quasi-cleavage.     

AZ31镁合金表面碱性化学镀镍工艺研究

试验研究了AZ31镁合金表面碱性化学镀镍工艺。采用扫描电镜(SEM)、能谱成分分析(EDS)和X射线衍射(XRD)等方法对镀镍层的表面形貌、镀层成分及物相结构进行了分析,并测定了AZ31镁合金及镀层在w(NaCl)=3.5%的水溶液中的腐蚀电位和极化曲线,以此评价镀层的耐腐蚀性能。结果表明,预镀镍层为晶格畸变的晶态低磷镀层,二次镀镍层为非晶态高磷镀层,镁合金表面腐蚀电位在化学镀镍后明显升高,二次镀镍后钝化电位范围明显扩大,其耐腐蚀性能明显优于预镀镍层的。     

钛离子注入对AZ31镁合金表面力学性能及耐蚀性的影响

对AZ31镁合金表面进行了钛离子注入试验,研究了钛离子注入对于镁合金表面改性层的影响。通过XRD、XPS研究了改性层的相结构和元素分布,通过硬度和摩擦磨损试验研究了改性层的力学性能。结果表明,经过钛离子注入之后,改性层中并无新相生成;当注入剂量为2.5×1017ion/cm2时,改性层深度可以达到160 nm,改性层中Ti呈高斯分布,存在形式从外到内为TiO2向Ti过渡。经过钛离子注入之后,镁合金表面硬度大大提高;改性层的摩擦因数并没有降低,但是耐磨性有所提高。随钛离子注入剂量的增加,改性层的耐腐蚀性能呈先上升后下降趋势。     

Effect of surface pretreatment on corrosion resistance and bond strength of magnesium AZ31 alloy

A phosphate-permanganate surface treatment with additives Na₂MoO₄ and NaF was developed to improve the corrosion resistance and bond strength of magnesium AZ31. The phosphate coatings which have the magnesium phosphate, MgO, Mg (OH)₂, MgF₂ and a minor of Al₂O_3, Al(OH)₃ Al_0.35−0.55Si_0.10−0.48P_0.13−0.35O_2.1−2.2 and, Al_0.35S_i0.48P_0.18O_2.2, and Al_0.52P_0.48O_2.2 were formed on the surface of magnesium AZ31. A combination addition of the Na₂MoO₄ and NaF in the phosphate solution improves the corrosion resistance and bond strength of phosphated magnesium alloys. The optimal contents of NaF and Na₂MoO₄ are 0.8 g/L and 0.5 g/L, respectively.     

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。     

微弧表面处理对AZ31B镁合金耐腐蚀及耐腐蚀疲劳性能的影响

采用微弧表面处理技术(微弧氧化MAO和微弧复合MCC)在AZ31B镁合金基体上制备出不同断面结构的防护涂层。通过电化学腐蚀及腐蚀疲劳测试方法,研究了MAO、MCC涂层的电化学腐蚀及腐蚀疲劳性能。结果表明,生长10 min的MAO涂层具有较好的耐电化学腐蚀性能。MAO涂层表面存在微孔和微裂纹,在应力条件下微孔和微裂纹作为疲劳断裂的裂纹萌生点,可加速裂纹的萌生与扩展,使其腐蚀疲劳寿命相较AZ31B合金基体降低了55%。而具有MCC涂层的AZ31B合金试样腐蚀疲劳极限为(64.0±5.4) MPa,比AZ31B合金基体提高了59%。在低应力载荷下(＜80 MPa),微弧复合涂层试样的腐蚀疲劳强度得到明显提高。     

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.     

A new method for electroless Ni-P plating on AZ31 magnesium alloy

Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

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.     

镁合金AZ31无铬无氟无亚硝酸盐磷化膜的制备及耐蚀性能(英文)

以磷酸二氢锰和无氟、无铬、无亚硝酸盐的添加剂为主要成分,通过化学沉积的方法在镁合金AZ31表面获得致密均匀的耐蚀磷化膜。通过硫酸铜点蚀测试、SEM、XRD及电化学极化曲线等表征手段,详细研究了膜层的形貌、组成、相结构及耐蚀性能,讨论了成膜温度和游离酸对膜层微结构、形貌及耐蚀性能的影响。结果表明,磷化膜通过抑制阳极溶解和阴极析氢,有效地提高了镁合金AZ31的耐蚀性能。     

Phosphating process of AZ31 magnesium alloy and corrosion resistance of coatings

1 Introduction Magnesium alloys are relatively light structural materials, with excellent physical and mechanical properties,such as low densityand high specific strength, excellent castability and good machinability. These properties make them ideal cand…     

AZ31镁合金挤压管材力学性能测试

基于圆柱体弹性压缩和厚壁管受内压塑性变形的应力应变分析,得到了测试管件力学性能的方法。在WDW-100kN的试验机上对AZ31镁合金管材弹性内模胀形试验,测得该管材的屈服强度、抗拉强度及伸长率。     

Chemical conversion coating on AZ31B magnesium alloy and its corrosion tendency

The morphology change of the magnesium matrix after pre-treatment and the mor-phology as well as the phase composition of chemical conversion coating formed by phosphate were studied using scanning electron microscope and X-ray diffraction. The corrosion resistance of the coating was studied by salt spray and damp test, and the corrosion tendency during salt immersion test was analyzed. The results show that the phase composition before and after pre-treatment is almost change- less, and the deep microflaw appears between α and β phases during acidic pickling. The phosphate conversion coating is mainly composed of Mg, MgO, and some amor-phous phase, and it can provide a good protection for the AZ31B alloy. Results from corrosive morphology indicate that the growth and the corrosion resistance of the phosphate conversion coating are related to the forming process of the AZ31B matrix.     

AZ31B镁合金板材冲压成形性能研究

由于镁合金板材的冲压产品具有较好的力学性能和表面质量而成为镁合金材料应用的一个趋势。然而,目前它的许多成形性能参数尚未研究,这也影响了镁合金冲压成形工艺的设计。为丁研究镁合金薄板的冲压成形性能,试验得到了一些成形性能参数,并为镁合金冲压成形的有限元模拟提供了重要的试验参数。     

碳酸钠对搅拌摩擦加工AZ31镁合金缓蚀性能的影响

通过搅拌摩擦加工(FSP)手段,对3 mm厚的AZ31镁合金板材作表面加工处理.然后在质量分数为5%的NaCl腐蚀溶液中添加不同浓度的碳酸钠作为缓蚀剂,通过动电位极化曲线以及交流阻抗(EIS)测试,研究了室温下该缓蚀剂对镁合金母材及搅拌摩擦加工处理镁合金电化学行为的影响.结果表明,添加缓蚀剂后,FSP镁合金及母材的腐蚀电流密度均减小,极化电阻及电荷转移电阻均增大,而且FSP镁合金的缓蚀效率要优于母材的缓蚀效率,且随浓度的增加而增加,碳酸钠是一种有效的无机缓蚀剂,并且其缓蚀作用效果与金属表面状态密切相关.     

AZ31镁合金微弧氧化与有机镀膜的复合表面改性及功能特性

采用微弧氧化与有机镀膜技术对AZ31镁合金进行复合表面改性,分别对微弧氧化膜的形成过程及表面特征、微弧氧化膜表面有机镀膜过程、微弧氧化膜与复合膜的润湿性及耐腐蚀性进行研究.结果表明镁合金经微弧氧化改性后,由于表面具有微纳多孔粗糙结构,同时具有较高的表面自由能和极性分量,与蒸馏水接触时存在较强的范德华力和毛细管吸附力,且对强极性水分子具有很强的相溶性,使其蒸馏水的静态接触角接近0°,表现为超亲水特性;而微弧氧化膜表面再经有机镀膜复合改性后,具有较低的表面自由能,对强极性水分子具有一定的排斥作用,使其静态接触角达到113.7°,表现为疏水特性;微弧氧化膜经有机镀膜表面改性后,耐腐蚀性能明显改善,疏水复合膜层在0.1mol/LNaCl溶液中,与基体相比,其动电位极化腐蚀电流密度减小3个数量级,而电化学阻抗提高3个数量级,表现为类似纯电容行为.     

Microstructure and corrosion property of AZ61 magnesium alloy by electromagnetic stirring

The influence of permanent-magnet-driven stirring during solidification on the microstructure and corrosion property of AZ61 magnesium alloy was investigated. The corrosion behaviour of AZ61 was studied in 3.5mol/L NaCI by measuring electrochemical polarization. The results show that the permanent-magnet stirring refines the microstructure of AZ61 magnesium alloy, which improves the precipitation amount and distribution uniformity of β phase and decreases the content of hydrogen, but it has less influence on the distribution uniformity of Zn. The change of precipitation amount of β phase influences the corrosive nature of the matrix, and it has no direct proportion with the corrosion resistance of the matrix.     

Microstructural characteristics and corrosion property of non‐chromate surface treatments on AZ91D magnesium alloy

Chromate conversion coatings can be successfully used for corrosion protection of magnesium alloys. However, the environmental laws have imposed severe restrictions on chromate use in many countries. In this study, a novel protective environmental‐functionally gradient coating was formed on AZ91D magnesium alloy by non‐chromate surface treatments, which consisted of pre‐etching followed by cerium‐based chemical conversion before applying the sol–gel CeO₂ film. It was determined by the analysis of X‐ray diffraction that the gradient coating was mainly composed of CeO₂. The calculation, based on the Scherrer formula, further revealed the formation of nanocrystalline structure in the coating. Scanning electron microscopy (SEM) observations showed that the coating was homogeneous and compact, no obvious cracked structure occurred. According to the immersion tests, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) tests, the corrosion resistance of AZ91D magnesium alloy was found to be greatly improved by means of this novel environmental‐functionally gradient coating.