Influence of potential on structure and properties of microarc oxidation coating on Mg alloy

In order to obtain optimizing microarc oxidation coating on Mg alloy from a friendly-enviormental electrolyte free of Cr⁶⁺ and PO ₄ ³⁻ , constant potential regime was applied to produce it. The influence of potential on the morphology, composition, structure and other properties, such as microhardness and corrosion resistance were investigated by scanning electron microscopy (SEM), energy dispersive spectroscope (EDS), X-ray diffraction (XRD), hardness tester and electrochemical method. The results clearly show that oxidation potential plays an important role in the formation of coating’s structure and properties. The microarc oxidation coating is smooth and white, which consists of two layers. The external layer is loose and porous and enriched in Al and Si. Moreover, its content of Al and Si increases with the increasing operated potential. While the inner layer is compact and the content of Al and Si are lower than that of the external layer. The coating is composed of several phases and the major phases are MgAl₂O₄ and MgO, and the minor phases are Al₂O₃ and SiO₂ when the potential is higher. The microhardness of coating is obtained the maximum at the potential of 45 V, so does the corrosion resistance.     

Analyses of Microarc Oxidation Coating Formed on AZ91D Alloy in Phosphate Electrolytes

This paper studied the appearance transition of microdischarges, the phase composition and the morphology evolution of the oxide film formed by microarc oxidation on AZ91D magnesium alloy. The appearance of microdischarges population experienced apparent changes in size, spatial density and color, which was related with the changes of the type and quantity of the disintegrated gas bubbles generated at the interface between the electrolyte and substrate. Correspondingly, the diameter of micropores together with net-like fine microcracks increased when a higher voltage was employed. The coating was composed of MgO, MgAl2O4 and there existed a fluoride-enriched zone of about 3-5μm at the film/substrate interface.     

Ti6Al4V钛合金微弧氧化工艺研究

采用直流稳压电源,选用3种不同PH值的碱性微弧氧化电解液,在Ti6Al4V钛合金表面制备微弧氧化膜层;应用扫描电子显微镜分析微弧氧化膜层形貌特征。结果表明,钛合金微弧氧化膜层表面凹凸不平,带有微米级和亚微米级的孔洞,孔洞周围呈现火山丘状形貌特征;微弧氧化电解液PH值越大,火花放电时间越长;在给定电压条件下,电解液PH值越大,微弧氧化膜层厚度越大。     

Effects of KMnO4 on microstructure and corrosion resistance of microarc oxidation coatings on 2024 aluminum alloy

Microarc oxidation (MAO) coatings were prepared on 2024 aluminum alloy in a Na_2SiO_3-KOH electrolyte with KMnO_4 addition varying from 0 to 4 g/L. The microstructure and phases of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively. The corrosion resistance of MAO coatings was evaluated by electrochemical potentiodynamic polarization in 5% (mass fraction) NaCl solution. The results show that when KMnO_4 is added into base electrolyte, the growth speed of oxide coatings is increased obviously. The main phase of oxide coatings is Al_2O_3, and the contents of MnO_2 and Mn_2AlO_4 phases are increased at the top of oxide coatings with increasing the concentration of KMnO_4. The solute elements participate in forming the oxide coatings. When a proper concentration of KMnO_4 (2.5 g/L) is added into the base solution, the micropores of the MAO coatings are small and compact, and the corrosion resistance of oxide coatings is increased largely.     

Ti基体上形成微弧氧化膜组成和结构的研究

在甘油磷酸钙和醋酸钙电解液中采用直流电源对纯Ti进行了微弧氧化。采用微弧氧化方法所制备的氧化膜具有粗糙多孔的结构,且微孔直径随着电压的增加而增大。AES分析表明在基体与氧化膜界面发生了扩散,从基体钛到氧化膜的表面氧的浓度逐渐增大,钛的浓度逐渐减小。XPS分析表明氧化膜的组成随着所施加的微弧氧化电压而改变,微弧氧化电压为200V时TiO2、Ti2O3和TiO占Ti的原子百分比分别为72．61％、22．08％和5.31％;当微弧氧化电压为350V时氧化膜表面Ti元素只由TiO2、Ti2O3组成,且占Ti的原子百分比分别为85．48％、14．52％。     

微弧氧化技术在高压齿轮水泵中的应用

为了在良好的加工工艺和高性价比前提下,提高水压元件的摩擦磨损特性和耐蚀性能,利用微弧氧化技术在常规液压元件的工作表面制备陶瓷化涂层,使其能直接应用于水压传动系统.应用该技术在材质为ADC12的高压齿轮泵的浮动侧板表面原位生成致密的陶瓷氧化层,其厚度可达130m以上,硬度可达HV1000以上.将经过陶瓷化处理的高压齿轮泵用于水压传动试验表明,该泵工作运行稳定,最高出口压力可达16MPa.在现阶段整体工程陶瓷元件应用于水压传动尚不成熟的情况下,使用微弧氧化技术进行元件表面改性是一种经济可行的方法.     

挤压比对AZ91镁合金组织及力学性能的影响

研究了挤压比对热挤压AZ91镁合金显微组织和拉伸性能的影响.结果表明：热挤压可以显著细化AZ91镁合金的晶粒，而且随着挤压比的增加，晶粒变得更加细小；增大挤压比也可以提高AZ91镁合金在不同实验温度下的抗拉强度和屈服强度，且经过3种挤压比挤压的AZ91镁合金在150 ℃时均呈现最高的抗拉强度和屈服强度；此外，经不同挤压比挤压的AZ91镁合金的伸长率均随实验温度的升高而增加.通过拉伸断口形貌的扫描电镜分析，确定了热挤压AZ91镁合金在室温拉伸时均表现为解理断裂为主的脆性断裂，而在较高温度下拉伸时则基本呈现韧性断裂特征.     

Study on BaTiO_3 films prepared by AC power microarc oxidation

BaTiO3 films were prepared by microarc oxidation (MAO) with an in-house built alternating current (AC) power supply in Ba(OH)2 solution in this study. The surface morphology, combinability with the substrate and phase composition of the films were investigated by XRD, SEM and TEM. The BaTiO3 films were annealed at a temperature range of 900 to 1200℃ and phase compositions were tested thereafter. The results showed that the BaTiO3 films were mainly composed of the primitive hexagonal phase with relatively sm...     

不同Mg/Si比对含Zn的Al-Mg-Si合金再结晶组织及性能的影响

为改善Al-Mg-Si系合金汽车板综合性能,通过浇铸法制备出3组合金成分铸锭,并经过均匀化、热轧、中间退火、冷轧,获得1 mm厚的合金板材.合金板材经560℃固溶30 min后,立即在100℃条件下预时效8 h,室温停放14天,模拟铝板转运存储过程,并拉伸变形2%,再在185℃下进行20 min烘烤处理,实现烘烤硬化.采用金相显微镜、装备电子背散射衍射的扫描电镜对合金进行显微组织观察及织构分析,通过万能电子试验机进行力学性能测定,研究不同Mg/Si比和高Zn元素对合金再结晶组织及织构、烘烤硬化性以及腐蚀敏感性的影响.结果表明,Mg/Si比相等合金再结晶组织更加均匀细小,平均晶粒尺寸190μm,存在相对较少的Cube织构{001}100和较多的P型织构{011}122;高Mg合金、高Si合金局部晶粒粗大,Cube织构{001}100较多,P型织构{011}122较少;预时效后,Mg/Si比相等合金强度较高,且烘烤硬化性优异,烤漆硬化增量达到107 MPa;烤漆后,更多的Zn原子扩散到晶界上,强化晶界微电流反应,欠时效态Mg/Si比相等合金较高Mg合金、高Si合金抗腐蚀敏感性降低,被腐蚀深度为121μm.     

K438高温合金Al-Si涂层的高温氧化表面形貌分析

为提高航空发动机使用寿命,航空发动机涡轮机叶片表面均采用防护涂层技术,以提高基体合金的抗高温氧化腐蚀性能.采用热扩散的方法,在K438镍基高温合金表面制备了Al Si涂层.依据GB/T13303 91标准,对制备了Al Si涂层的K438高温合金进行了1 000℃×500h高温氧化性能试验.用XL 300FEG扫描电镜对氧化后的涂层表面进行观察分析,分析结果表明,K438高温合金表面的Al Si涂层,在高温氧化过程中已转变成连续致密的αAl2O3 氧化膜,该氧化膜无裂纹、剥落发生,可有效地阻止氧原子的渗入.涂层中Si元素的加入,能有效地阻止涂层元素与基体元素的互扩散,起到了扩散障的作用,延长了涂层的退化周期,使涂层获得了优良的抗高温氧化性能.     

海上风电机组用N38SH永磁体在盐雾中的性能

针对风电机组在生命周期内始终受到盐雾、湿热环境影响的问题,研究了发电机中永磁体在海洋盐雾环境下的性能变化.通过盐雾腐蚀试验,模拟发电机用N38SH永磁体的服役环境,研究其在盐雾腐蚀条件下磁性能的变化,为海上风电机组永磁体的保护提供理论依据.试验结果表明,无论有无镀层保护,盐雾腐蚀将极大程度影响永磁体的磁性能,特别是在剩余磁感应强度和矫顽力等性能指标下降较多时,需要专门的保护措施.     

镁合金化学镀Ni-W-P合金

将AZ91D镁合金无铬处理后,以硫酸镍和钨酸钠为主盐,柠檬酸钠和碳酸钠为复合络合剂,在碱性镀液中通过调整镀液组成,得到W含量较高的Ni-W-P合金镀层。此镀层中W及P的质量分数分别为4.50%和4.84%。通过孔隙率和极化曲线测量了此镀层的耐蚀性能,表明该镀层能够很好地提高AZ91D镁合金的耐蚀性。     

Microstructures and mechanical properties of Mg-Ce-Zn-Zr wrought alloy

Microstructures and mechanical properties of Mg-2.0 ?-0.7 % Zn-0.7% Zr alloy were studied. The results of scanning electron microscopy show that Mg12 Ce phase mainly distributes at the grain boundaries. The fine Mg12 Ce phase can apparently elevate recrystallization temperature by preventing the grain boundary migration. No dynamic recrystallization occurs during the hot-extrusion. The mechanical properties of as extruded specimens are σb=278.5MPa, δ=12.0%, while those of the specimens annealed at 250℃ for 100 h are σb=272.6 MPa, δ=11.3%, which indicate that the alloy has good mechanical properties at room temperature.     

铝合金化学镀镍磷合金结构和性能

针对质子交换膜燃料电池双极板的需要,以铝合金为基体材料,采用碱性和酸性双溶液体系化学镀镍磷合金.采用电子探针方法测定了镀层中镍磷含量,X衍射方法研究了热处理对镀层结构的影响,伏安法研究了热处理对镀层耐蚀性的影响.试验结果表明,热处理明显影响镀层的结构和耐蚀性,对于P含量为12.1%（质量）的镍磷合金镀层,经过200～250℃热处理后,晶化不明显但耐蚀等性能明显改善,可以用作质子交换膜燃料电池双极板.     

磷化液中ZnO对AZ61镁合金磷化膜的影响

探讨了锌系磷化液中主要的成膜物质ZnO的质量浓度对AZ61镁合金磷化膜的微观结构和性能的影响.利用金相显微镜、扫描电镜、能谱分析仪观察和分析了磷化膜的结构、表面形态和组成成分,并通过阳极极化曲线测量评价了磷化膜的耐腐蚀性能.结果表明:在低ZnO质量浓度的磷化液中,获得的磷化膜比较疏松且不完整,其并未表现出优异的耐腐蚀性;在高ZnO质量浓度的磷化液中,得到的磷化膜晶粒较粗大,厚度不均匀,耐腐蚀性不佳;在中等ZnO质量浓度2.0g／L的磷化液中,得到了均匀、完整的磷化膜层,极化曲线测量表明了其在质量分数为3.5％NaCl溶液中具有较好的耐腐蚀性.     

铝合金化学镀镍磷合金结构和性能

针对质子交换膜燃料电池双极板的需要，以铝合金为基体材料，采用碱性和酸性双溶液体系化学镀镍磷合金．采用电子探针方法测定了镀层中镍磷含量，X衍射方法研究了热处理对镀层结构的影响，伏安法研究了热处理对镀层耐蚀性的影响．试验结果表明，热处理明显影响镀层的结构和耐蚀性，对于P含量为12．1％（质量）的镍磷合金镀层，经过200—250℃热处理后，晶化不明显但耐蚀等性能明显改善，可以用作质子交换膜燃料电池双极板．     

FeNiMnCuC0．2Alx高熵合金结构及性能研究

通过高频感应加热在真空下制备FeNiMnCuC0．2Alx（x=0、0．1、0．2、0．5mol）高熵合金,对固溶处理后的试样进行结构及性能研究。结果表明,FeNiMnCuC0．2Alx高熵合金具有简单的面心立方结构;添加少量Al（x=0．1、0．2mol）能细化FeNiMnCuC0．2Alx高熵合金晶粒,但x=0．5mol时,晶粒又变得粗大;初生树枝状晶富含Fe、Ni元素,Mn、Cu在枝晶间相内有所聚集,C、Al大体上均匀分布于两相中;x=0时,FeNiMnCuC0．2Alx高熵合金具有高的抗压强度（5218MPa）,x=0．1mol时,舍金抗压强度（4037MPa）和压缩率（〉75％）均较佳,随Al添加量的继续增加,合金压缩性能有所下降,x=0．5mol时,合金表现为脆性断裂。     

Influence of Mg2N2 powder on microstructures and mechanical properties of AZ31 Mg alloy

In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% (mass fraction) Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added.Both A1N and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along (0001)Mg//(0001)AlN is 3.04%, which is very effective for heterogeneous nucleation.     

Al涂层对Ni基合金高温氧化性能的影响

为了研究Al涂层对Ni基合金高温氧化性能及氧化机理的影响,采用磁控溅射方法在Ni基合金表面制备了Al涂层,在600℃下对涂层进行了真空扩散退火和预氧化处理,并研究了涂层在1 100℃下的高温氧化性能.利用扫描电子显微镜和能谱仪分析了氧化膜的截面形貌及组成.结果表明,Ni基合金氧化动力学曲线近似服从抛物线规律,且合金的氧化增重最大.经过1 100℃高温氧化后,Ni基合金表面形成三层氧化膜,外层为Ni O、Cr_2O_3、Al_2O_3的混合氧化物和少量尖晶石氧化物,中间层主要为Ni的氧化物,内层为Al_2O_3.Al涂层试样的氧化增重相对较小,表明Al涂层在一定程度上提高了Ni基合金的抗氧化性能.     

钙对Mg-8%Al镁合金组织及性能的影响

为了提高镁铝合金的力学性能,通过扫描电镜（SEM）、x射线衍射仪等分析手段及室温与高温力学性能测试,研究了0.5%Ca对Mg-8%Al合金组织及力学性能的影响.结果表明,Mg 8%Al合金中加入0.5%Ca后,晶粒得到明显细化,沿α固溶体晶界分布的β-Mg-17-Al-12相变得细小、光滑,β-Mg-17-Al-12相周围的次生相消失;加入的钙除形成钙的化合物外,还有少量溶入β-Mg-17-Al-12中,基体中不含钙;0.5%Ca可使Mg-8%Al合金的室温及高温力学性能得到明显提高.