Gr/6061 Al复合材料环保型稀土耐蚀膜的研究

随着铝基复合材料的应用范围不断扩大,对其腐蚀性能方面的要求也更加迫切.传统铬酸盐钝化的方法因含有毒性的六价铬离子并致癌将被废除,因此开发绿色环保耐腐蚀涂层是当今材料研究领域的热点之一.采用含稀土Ce钝化防腐蚀膜层的工艺提高Gr/6061Al复合材料的耐腐蚀性,膜层无毒、无污染,具有环境保护作用.文章对环保型稀土Ce耐蚀膜的成膜工艺进行了研究,此工艺在Gr/Al复合材料表面覆盖完整,呈现"干泥"状分布于Gr/Al复合材料表面.EDS面扫描结果认定稀土Ce含量达47.48%(质量分数),Ce、O、Si、Al是组成膜的主要元素,膜层主要由稀土氧化物或氢氧化物组成.防腐蚀性测试表明,稀土转化膜试样的Ecorr比裸试样的Ecorr提高84 mV,说明稀土转化膜试样的防腐蚀性能较佳.无毒无污染的Gr/Al复合材料表面环保型稀土Ce转化膜是有希望进行工业化应用的理想涂层.     

高含量B_4C/Al6061复合材料微弧氧化机制及耐腐蚀性

用微弧氧化技术对30%B_4C/6061Al复合材料进行了表面改性处理,探索了该材料的微弧氧化机制、表面反应产物和形貌。结果表明:B_4C/6061Al复合材料表面生成了一层灰白色的Al_2O_3层,B_4C陶瓷粉末颗粒与基体6061Al微间隙得到闭合,其腐蚀电流密度降低约三个数量级,耐蚀性能高于未做表面微弧氧化的复合材料。     

SiC_p表面处理对SiC_p/6061Al复合材料性能的影响

为提高SiC_p/6061Al复合材料的性能,采用不同方法对SiC颗粒进行了表面处理,并通过直热烧结法制备了不同SiC表面改性状态的SiC_p/6061Al复合材料。研究表明:经过酸洗+高温氧化处理后SiC_p表面生成了一层Si O2膜,SiC_p的棱角发生钝化,颗粒形貌发生改变;经过碱洗+K_2ZrF_6处理后,SiC_p表面得到粗化,并在SiC_p表面析出K_2ZrF_6。对SiC_p进行不同表面处理后,制得的SiC_p/6061Al复合材料的性能都得到很大改善,而且碱洗+K_2ZrF_6处理这种表面处理方法对复合材料性能的改善效果最佳。     

铜盐黑色钝化

镀锌层黑色钝化膜具有均匀的乌黑外观、良好的结合力 ;耐蚀、耐磨性也比彩色钝化、高温或常温发黑等优越得多。本文结合产品和厂情分析后采用铜盐法黑色钝化工艺 ,现作简单介绍。1　铜盐黑色钝化工艺1.1　流　程钢铁制品→前处理→电镀锌→流动水清洗× 2→锌层常规出光→流动水清洗× 2→黑色钝化处理→流动水清洗→压缩空气吹干 (或浸脱水防锈剂 )→膜层老化处理→检验成品入库→不合格件返工处理。1.2　配　方[1]硫酸铜 (ＣｕＳＯ4 ·5Ｈ2 Ｏ) 30～ 5 0ｇ/Ｌ表面活性剂微量铬酐 (ＣｒＯ3 ) 15～ 30 ｇ/ＬｐＨ 2～ 3甲酸钠 (ＣＨＣＯＯＮ…     

含Ag抗菌双相不锈钢表面腐蚀产物的XPS分析

采用X射线光电子能谱技术(XPS)研究了含Ag抗菌双相不锈铸钢在有菌环境中经电化学极化后的表面腐蚀产物。结果表明:添加纯Ag颗粒制备的不锈钢经1150℃固溶处理后,其钝化膜表层中的Ag主要以Ag2+氧化物和游离态的形式存在,Cr主要以CrO2,CrO3和Cr(OH)3形式存在,而添加150～300μm Cu-Ag中间合金颗粒制备的不锈钢经1150℃固溶处理后,其钝化膜表层中的Ag主要以Ag2+,Ag+和Ag2/3+氧化物形式存在,Cr以CrO2、Cr2O3和CrO3等多价态铬氧化物形式共存,且与前者相比,添加150～300μm Cu-Ag中间合金颗粒制备的材料其钝化膜中Cr2O3、钼氧化物和MoO42-的含量更多,而α-FeOOH和Cr(OH)3等氢氧化合物以及水合物的含量更少,表明其钝化膜的稳定性优于添加纯Ag颗粒制备的材料。     

热压烧结Gr/6061Al复合材料制备与组织性能研究

实验采用了热压烧结的方法制备了1~25vol%片层石墨(Gr)含量的Gr/6061Al复合材料,并采用了纳米铝粉包覆片层石墨的混粉工艺提高片层石墨在铝基体粉末中的分散均匀性。所制备的复合材料中,片层石墨均匀分散在铝基体中,界面结合良好,未发现界面反应产物的存在,通过透射电镜观察到了少层石墨烯的存在。1~15vol% Gr含量的Gr/6061Al复合材料的致密度均高于90%;复合材料的致密度和摩擦系数随着片层石墨含量的增加具有相同的变化趋势,都逐渐降低;石墨含量从1vol%增加到25vol%时,复合材料摩擦系数(COF)呈逐渐降低的趋势;与1vol.%Gr含量的Gr/6061Al复合材料相比,其他Gr含量的复合材料的磨损率均较高。     

6063铝型材表面转化膜的制备

以K₂ZrF₆钝化液为成膜剂在建筑用6063合金表面制备了无Cr化学转化膜,通过钝化液浓度和钝化液温度的优化得到了膜层均匀和耐腐蚀性能良好的转化膜制备工艺,并研究了此工艺转化膜的组织与结构。结果表明,当K₂ZrF₆钝化液浓度为0.382 mol·L^-1、钝化液PH值为4.5、钝化液温度为25 ℃和钝化时间为15 min时可以在6063合金表面形成耐腐蚀性能良好的均匀膜层;转化膜层中主要含有Al、Al₂O₃、AlF₃、KZrF₃O·2H₂O和KZrF₃(OH)₂·H₂O相。     

Gr/Al复合材料表面化学镀镍沉积特性及耐蚀性

用化学镀镍法在Gr/Al复合材料表面沉积了Ni-P合金,研究其沉积特性及耐蚀性.结果表明,Gr/Al复合材料表面化学镀镍具有其特殊性:在前处理的活性质点形核时,基体铝合金从浸Zn溶液中置换出催化活性的Ni核:增强体石墨纤维可以吸附一定数量的Ni核,随后的化学镀镍时Ni-P合金就会在Gr/Al复合材料表面均匀沉积.表面化学镀镍通过阻挡腐蚀原电池反应中电偶腐蚀的导电路径以及形成非晶态的镀层结构,显著地提高了Gr/Al复合材料的耐蚀性,延长了使用寿命.     

钝化时间对Fe30Mn9Al合金钝化膜半导体特性影响

运用电化学阳极钝化技术对Fe30Mn9Al合金在1 mol/L Na_2SO_4溶液中进行不同时间的表面钝化处理;利用俄歇电子能谱(AES)、X射线光电子能谱(XPS)表面分析技术及Mott-Schottky曲线测试技术研究钝化时间对Fe30Mn9Al合金钝化膜的组成结构与半导体特性的影响。结果表明:Fe30Mn9Al合金在1 mol/L Na_2SO_4溶液中钝化15 min所得钝化膜分为内外2层,外层具有n型半导体特征,由Fe_2O_3、Al_2O_3、Mn_2O_3、FeOOH和AlOOH组成,内层具有p型半导体特征,由MnO组成。随着钝化时间由15 min增至5 h,钝化膜中的MnO溶解,Mn含量降低,Fe、Al填充Mn留下的空位在膜内富集,Fe、Al氧化物转变为Fe、Al氢氧化物,钝化膜由FeOOH、AlOOH和Mn_2O_3组成,具有n型半导体特征。与钝化15 min所得钝化膜相比,钝化5 h所得钝化膜的施主浓度ND由2.58′10~(21) cm~(-3)降至1.96′10~(21) cm~(-3),平带电位Efb由–283 mV降至–366 mV,钝化膜的保护性能提高。     

镀锌层三价铬黑色钝化膜的耐蚀性能

制备了一种环保、不含六价铬的三价铬黑色钝化液,选择适当的封闭剂,研究其在镀锌层表面钝化后的耐腐蚀性能。通过醋酸铅点滴试验、塔菲尔极化曲线测试、电化学阻抗测试检测钝化膜的耐蚀性及采用扫描电子显微镜观察其表面形貌。结果表明:镀锌层表面经三价铬黑色钝化后再进行封闭处理,弥补了Cr3+钝化后无自愈能力的缺点,显著提高了镀锌层钝化膜的耐腐蚀性能,而且达到了Cr6+黑色钝化的外观效果。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.