MB8镁合金植酸转化膜的制备及性能

通过单因素实验优化镁合金植酸转化工艺,发现在植酸体积浓度为10 mL/L,pH=2.5,温度50℃,成膜时间20 min条件下,可在MB8镁合金表面制备出均匀一致的植酸转化膜.该膜层微观形貌与铬酸盐转化膜类似,表面呈现出均匀分布的网状微裂纹,类似于"龟裂的土地",膜层主要成分为Mg,O,P,Mn和C;动电位极化曲线测试...     

钙对镁合金表面锰系转化膜的影响

将钙离子作为添加剂,加入到镁合金锰系转化膜成膜溶液中.应用粗糙度仪和电化学方法研究钙离子对膜层粗糙度和膜层耐蚀性的影响规律;应用SEM和XPS分析钙离子对膜层表面形貌影响、膜层的元素组成和钙离子的存在形式.结果表明:Ca(N03)2浓度大于2g/L后,膜层粗糙度较未添加前有所降低,膜层表面组织变得平整,膜层裂纹变得窄小;Ca(N03)2浓度为5g/L时,膜层的耐蚀性最好.XPS结果表明,膜层主要由Mn、P、O、Mg、Ca和Al元素组成,钙离子在膜层中以CaC03、CaO和一种无定形态磷酸钙盐存在.     

pH对Az31B镁合金植酸转化膜的影响研究

采用析氢实验及Tafel极化曲线研究了AZ31B镁合金在不同pH植酸溶液中成膜时的反应速率和转化膜的防腐性能,并用SEM,AFM,EDS.FTIR观察和检定转化膜形貌、元素组成及官能团构成.结果表明溶液的pH=1时,植酸与镁合金的反应剧烈,转化膜有大量的裂纹;pH=4和pH=6时.反应速率很慢,成膜均匀并较少裂纹,但转化膜较薄;pH=2时,反应速率较为和缓.转化膜表面较为平整.有呈网格状结构的大量细小裂纹.此时,所形成的植酸转化膜具有最佳的防腐性能.此外.植酸转化膜由较薄的内层及具有一定裂纹的外层所组成,转化膜含有Mg.Al,zn,C.O.P元素及PO_4~-3,HPO_4~2-.OH~-基团.     

Mn（NO3）2/Na2MoO4对AZ31B镁合金表面磷化膜微观形貌及耐蚀性的影响

以AZ31B镁合金为基体,通过化学沉积的方法分别在添加Mn(NO3)2,Na2MoO4以及复配的锰系磷化溶液中获得了磷酸盐转化膜。采用扫描电子显微镜(SEM)、电化学工作站及CuSO4点滴等表征手段,研究添加剂对磷化膜表面微观形貌和耐蚀性的影响。结果表明:Mn(NO3)2含量在0~2 g/L之间增加时,磷化膜晶粒尺寸先减小后增大,耐蚀性先增大后降低;Na2MoO4含量在0~0.5 g/L之间增加时,磷化膜晶粒尺寸显著减小,然后增大,耐蚀性显著提高;Mn(NO3)2和Na2MoO4复配后膜层致密,耐蚀性增强,但差于单独引入Na2MoO4的改善效果。综合比较分析,Mn(NO3)2对锰系磷化膜耐蚀性的改善作用较小,而添加0.25 g/L的Na2MoO4获得的膜层更均匀细致,耐蚀性能更佳。     

成膜温度对AZ91D镁合金表面植酸转化膜的影响

利用Tafel曲线、阻抗谱分析、NaCl水溶液点滴实验和扫描电镜观察等手段,研究了温度对AZ91D镁合金的植酸转化膜表面形貌及耐蚀性的影响.结果表明:当温度为25℃～35℃时转化膜的耐蚀性较好,温度过高或过低都会使转化膜的耐蚀性变差;转化膜表面的裂纹是在干燥处理过程中由于表层转化膜体积收缩而产生的;镁合金表面形成的植酸转化膜应属于电子导体,该层膜的形成阻碍了腐蚀介质与镁合金基体的接触,同时抑制腐蚀产物的扩散,对镁合金起到了较好的防护作用.     

压铸镁合金无铬转化的工艺探讨

为了改善镁合金无铬转化膜耐蚀性能,采用正交试验法确定压铸镁合金无铬转化的优化处理工艺,讨论了工艺参数对转化膜性能的影响机制,并通过SEM,EDS,XRD等方法分析了优化工艺转化膜的微观形貌、化学成分和相组成。研究表明：当A剂80g／L;B剂2g／L;C剂1g／L时转化膜的耐蚀性能最佳;在优化工艺条件下,转化膜由底层、致密的中间层以及由大量的宽度为1～3μm纵横交错的“裂纹”所分割成的小岛表层组成。表面成分由Mg,Al,O,P及少量的Ca和V元素组成,物相则主要由Mg,Mg17A112及不定形相组成。     

镁合金表面植酸转化膜研究Ⅱ.pH值对镁合金植酸转化膜的影响

通过SEM观察、AES元素深度分析、成膜增重实验、动电位极化曲线和EIS电化学测试，研究了植酸处理液的pH值对AZ91D镁合金转化膜生长速度及耐蚀性的影响.结果表明：溶液在pH=8时，转化膜生长速度最快，膜层较厚，且完整，无碎裂；pH=12时，转化膜生长速度较慢，膜层较薄；pH=5时，转化膜生长速度最慢，有碎裂.当植酸溶液的pH值在5～12时，镁合金表面形成的转化膜均可提高其耐蚀性，且pH=8时形成的膜耐蚀性最好.     

成膜时间对镁合金镧盐转化膜耐蚀性的影响

稀土盐转化膜是一种绿色环保的金属表面处理技术,为探究硝酸镧成膜时间对镁合金耐蚀性的影响,在镁合金表面成功制备出不同成膜时间下的镧盐转化膜。 试验采用扫描电镜(SEM)、能谱仪(EDS)以及 X 射线衍射仪(XRD) 对膜层的表面形貌及组成进行了表征,采用点滴试验、电化学方法(EIS / Tafel)对不同成膜时间下膜层的耐蚀性进行了测试,并使用软件对结果进行拟合。 试验结果表明,镁合金表面生成了一层微米级的稀土转化膜,转化膜表面存在裂纹,其中 30 min 成膜时间的裂纹最小;点滴试验及电化学测试结果表明镧盐转化膜能够大幅度地提高镁合金耐蚀性, 30 min 成膜时间获得的膜层耐蚀性最佳,相对于空白镁合金,其自腐蚀电流密度下降了 4 个数量级,自腐蚀电位正移了 943 mV;EDS 结果表明,膜层主要由 La 和 O 元素组成,XRD 结果进一步表明 La(OH)₃ 是膜层的主要成分。     

老化时间对AZ31B镁合金铁氰化钾转化膜耐蚀性的影响

目的 在镁合金表面制备一种新型的化学转化膜,以提高其耐蚀性。方法 通过化学浸渍法,以铁氰化钾作为成膜主盐,在镁合金表面制备一层耐蚀性较好的化学转化膜,主要探究老化时间对AZ31B镁合金铁氰化钾转化膜耐蚀性的影响。利用扫描电镜（SEM）、X射线光电子能谱仪（XPS）、X射线衍射仪（XRD）和能谱仪（EDS）对膜层表面形貌及组成进行分析表征,利用电化学方法和析氢实验研究转化膜的耐蚀性能,利用浸泡实验探究膜层的寿命。结果 镁合金基体表面生成了一层具有较少裂纹的膜层,膜层厚度约为20μm。XPS、XRD及EDS结果表明,膜层主要成分为Fe₄[Fe（CN）₆]₃。动电位测试结果显示,老化12 h的膜层耐蚀性最佳,相比于未经处理的镁合金试样,其自腐蚀电位正移了约1000mV,自腐蚀电流密度下降了约3个数量级。电化学交流阻抗结果显示,老化时间为12 h的电荷转移电阻（Rct）最大,为41 380Ω·cm²,相比于其他老化时间的试样有了显著的提升。析氢实验结果也证明,老化12h的铁氰化钾转化膜明显提高了AZ31B镁...     

镁合金锌系磷酸盐化学转化膜的研究

目的优化镁合金锌系磷酸盐化学转化膜的制备工艺。方法制备锌系磷酸盐化学转化膜,采用点滴实验、电化学测试对化学转化膜进行耐蚀性评价,并通过激光共聚焦显微镜、扫描电子显微镜(SEM)和X射线衍射仪(XRD)对膜层进行表征,研究主盐、温度和添加剂对镁合金锌系磷酸盐化学转化膜的影响。结果转化溶液中氧化锌、磷酸、氟化钠、酒石酸钠的浓度对转化膜的耐蚀性和膜厚具有较大影响,在一定浓度范围内,转化膜的耐蚀性随浓度的增加而增大。转化膜耐蚀性随温度的升高先增加后下降,50℃时点滴时间达到59 s,膜层相对致密,缝隙较小。选取的添加剂中,EDTA能明显提高膜层的耐蚀性,膜层均匀致密,加入0.3 g/L EDTA的转化膜的腐蚀电位比未加添加剂的转化膜正移0.05 V,点滴时间提高到68 s。镁合金锌系磷酸盐转化膜主要成分为Zn_3(PO_4)_2+Zn_2Mg(PO_4)_2+AlPO_4+Al_(12)Mg_(17)。转化膜的电化学阻抗半径大,自腐蚀电流密度低(2.594×10~(-6) A/cm~2),腐蚀电位正移较明显,耐蚀性更好。转化膜粗糙度小(2.396μm),平整光滑。结论镁合金锌系磷酸盐转化最优配方及工艺为:氧化锌2.0 g/L,磷酸12 g/L,氟化钠1.0 g/L,酒石酸钠4.0 g/L,EDTA 0.3 g/L,转化温度50℃,转化时间20 min。转化溶液加入EDTA后,能够明显提高转化膜的耐蚀性。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。