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AZ91D镁合金微弧氧化低能耗的电解质配方研究 总被引:1,自引:0,他引:1
利用自制微弧氧化装置在铝酸盐体系中对AZ91D镁合金进行微弧氧化处理.采用多重正交试验,从考察膜层厚度、单位能耗和耐蚀性出发,确定了AZ91D镁合金在铝酸盐体系中的最佳工艺参数.结果表明:在最佳电解质配方下,处理过程工作电压约在120 V,电流密度可以低到0.5 A/dm2,生长1 μm陶瓷涂层的单位面积能耗仅为456 W/(m2·μm).微弧氧化膜呈多孔结构、孔径较小,裂纹较少,分布均匀,膜层较为致密;微弧氧化膜由MgO和MgAl2O4组成;处理后AZ91D镁合金样品的腐蚀电流密度为0.014 μA/cm2,比未处理合金降低了接近3个数量级. 相似文献
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对AZ31B镁合金和6061铝合金异质金属铆接件进行了微弧氧化,研究了不同时间微弧氧化膜的微观形貌、物相组成、电化学性能、硬度等,对比分析了微弧氧化过程中镁合金、铝合金表面氧化膜的形成过程。结果表明:经过10min的微弧氧化后,该连接件整体被氧化膜包裹,氧化膜与2种合金基体均紧密连接,且均由致密层和疏松层组成;镁合金表面氧化膜主要由MgO、少量硅酸盐和氟化物组成,而铝合金表面氧化膜主要由Al_2O_3及少量硅酸盐组成;微弧氧化提高了连接件中镁合金、铝合金的腐蚀电位,降低了二者的腐蚀电位差,有效缓解了电偶腐蚀的发生。 相似文献
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本文主要通过微弧氧化工艺优化了AZ31B镁合金的腐蚀性能。在硅酸盐电解液里边,通过改变微弧氧化频率、占空比、电流密度、微弧氧化时间做了四因素三水平的正交实验,发现当频率为1000Hz、占空比为20%、电流密度为1.2A、时间为10min时,膜层自腐蚀电位最低。相较于镁合金基体,自腐蚀电位增加了522mV,极大的降低了镁合金自发性腐蚀的倾向性,因此提高了AZ31B镁合金的耐蚀性。 相似文献
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在添加不同含量Na2CO3和C6H12O6的NaOH-Na2SiO3-Na2B4O7基础电解液中,对AZ31镁合金进行直流阳极氧化处理,研究了镁合金阳极氧化膜的微观结构以及在中性盐雾中的耐腐蚀性能。结果表明:镁合金阳极氧化膜主要由MgO相和Mg2SiO4相组成;电解液中添加Na2CO3和C6H12O6后,阳极氧化膜表面微孔分布均匀且尺寸减小,阳极氧化膜厚度增加;当Na2CO3质量浓度由10g·L^-1增加到30g·L^-1时,微孔尺寸增大,氧化膜厚度减小;当C6H12O6质量浓度由5g·L^-1增加到15g·L^-1时,微孔尺寸减小,阳极氧化膜厚度增加;镁合金阳极氧化膜的主要腐蚀形式为点蚀,呈河流状花样分布;电解液中添加10g·L^-1 Na2CO3时,阳极氧化膜表面微孔最细小,孔径为1~3μm,阳极氧化膜厚度达16μm,阳极氧化膜具有较好的耐腐蚀性能。 相似文献
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微弧氧化是一种新兴的表面处理技术,利用微弧氧化技术在铝及铝合金材料表面生成陶瓷层,该膜层耐磨,耐腐蚀,耐高温冲击等性能明显优于传统阳极氧化膜.本文对试件厚度与LY12-CZ铝合金微弧氧化膜层厚度关系进行了研究.研究表明,试件厚度影响微弧氧化后不同膜厚的试件疲劳特性,试件厚度为2 mm时,膜厚10~20 μm微弧氧化对试件疲劳寿命有提高;试件厚度3 mm时,膜厚10~25 μm,微弧氧化使试件疲劳寿命略有降低;预腐蚀疲劳实验表明,微弧氧化试件腐蚀疲劳寿命比普通阳极化试件的腐蚀疲劳寿命高. 相似文献
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AZ91镁合金表面微弧氧化膜微观结构的TEM表征 总被引:1,自引:0,他引:1
在硅酸盐碱性电解液中,以AZ91镁合金为基体采用恒电流控制模式制备出微弧氧化陶瓷薄膜,采用透射电镜对微弧氧化膜的微观结构进行了分析,并测试了相关性能。结果表明:镁合金在以硅酸盐溶液为主的电解液中进行微弧氧化形成的产物主要是纳米晶MgO和MgAl2O4,并且形成了少量的非晶态物质和一定比例的较粗大MgO、MgAl2O4和MgSiO3晶粒,但这些粗大晶粒尺寸也在100~300 nm之间;形成的晶粒之所以如此细小主要是由于微弧氧化过程是一个快速烧结和快速冷凝的过程;制备的氧化膜在中性盐雾36 h后的腐蚀率小于0.09 g.cm-2.d-1,而显微硬度在1 000 HV以上。 相似文献
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铝合金微弧氧化陶瓷膜形成电解液组分优化 总被引:1,自引:0,他引:1
基于非对称双向脉冲电源,用L9(34)正交试验法优化了电解液组分。用扫描电镜(SEM)和X射线衍射(XRD)观察和分析了陶瓷层的组织特征和物相组成,并用点滴和全浸试验衡量膜层的耐腐蚀性。较佳的电解液配方为:磷酸盐15 g/L,硅酸盐10 g/L,碳酸盐5 g/L,络合剂4 g/L。膜层的相组成和耐腐蚀性与电解液的浓度密切相关,当浓度较低时,膜层由晶态Al2O3组成;当浓度较高时,膜层由含有较多显微裂纹的非晶态Al2O3组成;当浓度适中时,可获得主要由非晶态组成的致密Al2O3陶瓷层,该膜层表现出优异的耐腐蚀性能。 相似文献
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脉冲频率对钛合金微弧氧化膜的影响 总被引:1,自引:0,他引:1
采用交流微弧氧化法于NazSiO3和Na3PO4的混合溶液中,在Ti6Al4V钛合金表面制备了氧化物陶瓷膜;研究了脉冲频率对氧化膜厚度、表面形貌、物相组成和耐腐蚀性能的影响.结果表明:随着脉冲频率的增高,氧化膜的厚度逐渐减小,氧化膜表面的孔径尺寸减小,微孔数量逐渐增多;氧化膜主要由锐钛矿相和金红石相两种TiO2组成,当脉冲频率低于500 Hz时,频率对氧化膜各相含量的影响不明显;当脉冲频率超过500 Hz时,随着频率的增高,氧化膜中金红石相TiO2的含量稍有增加;表面覆盖氧化膜的Ti6Al4V钛合金在30%硫酸中的耐腐蚀性能比表面未覆盖氧化膜的有明显提高. 相似文献
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To study the requirements of the power supply in micro-arc oxidation (MAO) of magnesium alloy, many experiments were performed under the DC, unipolar, and ambipolar pulse output modes. Based on the experimental results and electric arc theory, the separate local arc discharge mechanism was put forward. It is considered that magnesium MAO process consists of three stages including anodic oxidation, micro-arc oxidation, and large-arc discharge in turn with increasing source voltage. The MAO film is composed of metal oxides that resulted from numerous discrete local arc discharges, which accumulate the non-equilibrium structure after undergoing sudden heating and cooling cycles. Separate local arc discharge is caused by the process in which the oxygen-based gas is ionized in the conduct channel bearing electric field intensity, changed from insulator to conductor that presents sharp negative resistance effect, and produced partially high temperature to ignite locally metal oxidation. The local arc discharge model is described as four courses: gas created from electrolysis, arc discharge, metals oxidization, and cooling and shrinking of oxides. The purpose of pulse supply is to inhibit the large-arc discharge by intervening proper cooling time, which cannot be actualized by a unipolar pulse mode because of the strong capacitive load characteristics but can be reached by an ambipolar pulse supply because the negative pulse period acts as cooling time. Using a discharge loop to remove the influence of load capacitive, a new type of pulse power supply for MAO is developed, so that the large-arc problem is resolved effectively, the film-forming efficiency is improved, and the pollution of the film and electrolyte caused by negative voltage is avoided. 相似文献
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To study the requirements of the power supply in micro-arc oxidation (MAO) of magnesium alloy, many experiments were performed
under the DC, unipolar, and ambipolar pulse output modes. Based on the experimental results and electric arc theory, the separate
local arc discharge mechanism was put forward. It is considered that magnesium MAO process consists of three stages including
anodic oxidation, micro-arc oxidation, and large-arc discharge in turn with increasing source voltage. The MAO film is composed
of metal oxides that resulted from numerous discrete local arc discharges, which accumulate the non-equilibrium structure
after undergoing sudden heating and cooling cycles. Separate local arc discharge is caused by the process in which the oxygen-based
gas is ionized in the conduct channel bearing electric field intensity, changed from insulator to conductor that presents
sharp negative resistance effect, and produced partially high temperature to ignite locally metal oxidation. The local arc
discharge model is described as four courses: gas created from electrolysis, arc discharge, metals oxidization, and cooling
and shrinking of oxides. The purpose of pulse supply is to inhibit the large-arc discharge by intervening proper cooling time,
which cannot be actualized by a unipolar pulse mode because of the strong capacitive load characteristics but can be reached
by an ambipolar pulse supply because the negative pulse period acts as cooling time. Using a discharge loop to remove the
influence of load capacitive, a new type of pulse power supply for MAO is developed, so that the large-arc problem is resolved
effectively, the film-forming efficiency is improved, and the pollution of the film and electrolyte caused by negative voltage
is avoided. 相似文献
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Most researches on micro-arc oxidation mainly focus on the application rather than discovering the evolution of residual stresses. However, residual stresses in the surface coatings of structural components have adverse effects on their properties, such as fatigue life, dimensional stability and corrosion resistance, etc. The micro-arc oxidation ceramic coatings are produced on the surfaces of 6061 aluminum alloy by a homemade asymmetric AC type of micro-arc oxidation equipment of 20 kW. A constant current density of 4.4___0.1 A/dm2 and a self-regulated composite electrolyte are used. The micro-arc oxidation treatment period ranges from 10 min to 40 min, and the thickness of the ceramic coatings is more than 20 Bin. Residual stresses attributed to 7-A1203 constituent in the coatings at different micro-arc oxidation periods are analyzed by an X-ray diffractometer using the sin2~u method. The analysis results show that the residual stress in the ceramic coatings is compressive in nature, and it increases first and then decreases with micro-arc oxidation time increase. The maximum stress value is 1 667_+20 MPa for period of 20 min. Through analyzing the coating thickness, surface morphology and phase composition, it is found that the residual stress in the ceramic coatings is linked closely with the coating growth, the phase composition and the micro cracks formed. It is also found that both the heat treatment and the ultrasonic action release remarkably the residual compressive stress. The heat treatment makes the residual compressive stress value decrease 1 378 MPa. The ultrasonic action even alters the nature of the residual stress, making the residual compressive stress change into a residual tensile stress. 相似文献
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In this study, a hydroxyapatite composite coating was prepared by a sol–gel technique on the micro-arc oxidation (MAO)-coated AZ31 Mg alloy to seal the micro-pores. The composite coating achieved a larger hardness value and two times thickness more than pure MAO coating. The corrosion and wear resistance of the sol–gel/MAO coating in simulated body fluid were investigated compared to MAO coating. It was found that the composite coating presented a positive corrosion potential and a lower corrosion current density than MAO coating. The sol–gel/MAO composite coating could provide more effective barrier against corrosive ions than single MAO coating for AZ31 alloy. In the wear tests, a ball-on-disk tribometer was used to study the effect of loads on the wear properties of the coatings at 37 °C. The wear resistance of sol–gel/MAO composite coatings was apparently superior to MAO coating. The wear mechanisms of abrasion and adhesion in composite coatings are investigated. Finally, two physical models for the corrosion and sliding wear mechanisms of sol–gel/MAO composite coatings are proposed, respectively. 相似文献
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Friction and wear properties of duplex MAO/CrN coatings sliding against Si3N4 ceramic balls in air, water and oil 总被引:2,自引:0,他引:2
It is evident that the micro-arc oxidation (MAO) ceramic coatings often exhibit relatively high friction coefficients as sliding against many mating materials. To reduce the friction coefficient for the MAO coatings, the duplex MAO/CrN coatings were deposited on 2024Al alloy using combined micro-arc oxidation and reactive radio frequency magnetron sputtering. The microstructure and phase of the duplex coatings were observed and determined using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The friction and wear behaviors of the duplex coatings sliding against Si3N4 balls in air, water and oil were investigated using a ball-on-disk tribometer. The wear rate of the duplex coating was determined by non-contact optical profilometer and the wear tracks on the duplex coatings were observed by SEM. The results showed the CrN coatings mainly consisted of Cr, CrN and Cr2N phases. The duplex coatings/Si3N4 tribopair exhibited the highest friction coefficient in air, while displayed the lowest friction coefficient in oil. When the normal load and the sliding speed increased, the friction coefficient in air increased from 0.65 to 0.72, whereas decreased from 0.58 to 0.36 in water and 0.20 to 0.08 in oil. The specific wear rates for the duplex coatings in air were higher than those in oil. In comparison to the MAO coatings, the duplex MAO/CrN coatings displayed excellent tribological properties under the same conditions. 相似文献