Zn-Al伪合金涂层的耐蚀性能研究

目的提高电弧喷涂锌铝合金涂层中Al的含量。方法用纯铝丝和Zn80Al20合金丝在Q235钢表面制备Zn-Al伪合金涂层,通过中性盐雾试验和电化学试验,与纯铝涂层和Zn-Al合金涂层进行对比,分析比较三种涂层在氯离子存在环境中的腐蚀行为。结果 Zn-Al伪合金涂层表现出了较高的活化能力和较低的腐蚀速度。结论 Zn-Al伪合金涂层的耐蚀性能优于纯铝涂层和Zn-Al合金涂层。     

溶剂的含量对高耐蚀锌基涂层的耐蚀性的影响

利用片状锌粉、铝粉、铬酐及其它有机物配制的新型高耐蚀锌基涂料具有良好的结合力和耐蚀性,并主要讨论了溶剂含量对锌基涂料的耐蚀性的影响.涂层的耐蚀性采用中性盐雾试验和5%盐水浸润试验,并测试涂层的阳极极化曲线综合进行比较.     

磁悬浮道岔Zn-Al防护涂层的研究及应用

目的设计和制备高性能热喷涂Zn-Al合金防护涂层,为其在磁悬浮道岔上的应用提供必要的理论基础,提高磁悬浮道岔的耐蚀性能,延长道岔的使用寿命。方法采用3种丝材火焰喷涂工艺,分别在Q235B钢基体表面制备了Zn-Al合金涂层。通过磁性测量方法、中性盐雾腐蚀试验和划格附着力测试,分析比较这3种工艺条件下制备的Zn-Al合金涂层的厚度、耐蚀性能和附着力。结果热喷涂Zn-Al合金涂层表面光滑,在其他工艺参数不变的情况下,当火焰喷涂距离逐渐减小,喷涂的道数逐渐增加时,热喷涂层的厚度随之增加。当喷涂距离为150 mm、喷涂道数为10时,热喷涂层的厚度最大,为126μm。涂层厚度的增加提高了涂层的耐蚀性能,并且涂层的附着力保持为1级。采用保守计算可知,厚度为126μm的热喷涂Zn-Al涂层的理论防腐寿命可以达到40年。结论热喷涂Zn-Al合金涂层对基体兼具有屏蔽和阴极保护的双重防护作用,保护性能较好,延长了磁悬浮道岔的使用寿命,降低了道岔的维修和维护成本。通过对工艺参数的分析和比较,确定了最佳的热喷涂工艺参数。该工艺条件下制备的热喷涂层结合强度高,耐蚀性能好。     

烧结NdFeB表面等离子喷涂Al防护涂层制备工艺及性能研究

目的 采用大气等离子喷涂工艺在烧结NdFeB磁体表面制备Al防护涂层,实现NdFeB磁体防护强化。方法 通过不同喷涂工艺制备Al涂层,采用扫描电子显微镜观测涂层表面、截面形貌和堆积厚度,利用垂直拉拔法测试最佳工艺下涂层的结合强度。喷涂不同厚度Al防护涂层,采用电化学工作站和中性盐雾腐蚀试验研究涂层的耐腐蚀性能,利用脉冲磁场磁强计对比分析喷涂Al涂层厚度对磁体磁性能的影响。结果 喷涂电流从400 A提高至600 A,当喷涂电流为500 A时,涂层表面致密,无明显溅射堆垛和未熔颗粒;喷涂30次,涂层厚度达到40 μm,结合强度达15.5 MPa。等离子喷涂Al防护涂层对NdFeB基体构成牺牲阳极保护,不同厚度涂层的自腐蚀电位无明显差异,约为–1.1 V,自腐蚀电流密度相对NdFeB基体降低了2个数量级。随着涂层厚度的增加,Al防护涂层的耐腐蚀性能逐步提高,喷涂厚度的70 mm的Al防护涂层耐中性盐雾腐蚀时间最高可达300 h以上。随着Al涂层厚度从0 μm增加至70 μm,磁体矫顽力略有提升,剩磁降低为原始样的2.0%~4.26%。结论 等离子喷涂技术可极大改善NdFeB磁体的耐腐蚀性能,为NdFeB防护的工业应用提供了新思路。     

钛钢复合板端面冷喷涂钛涂层的制备及性能研究

目的 改善钛钢复合板端面部位的服役性能。方法 采用冷喷涂技术在钛钢复合板端面制备了钛金属涂层。通过X射线衍射分析、热场发射扫描分析、能谱分析、维氏硬度测试、结合力试验、摩擦磨损试验、电化学测试和盐雾试验等手段,研究了冷喷涂过程中,送粉气体压力和温度对钛涂层的组织结构、显微硬度、耐磨性能、结合力和耐蚀性能的影响规律,以获得综合性能优异的钛涂层。结果 冷喷涂钛涂层具有良好的耐磨性能,送粉气体压力增大和温度升高可提高涂层的致密度,降低涂层孔隙率并提高涂层的显微硬度,改善涂层与基体间的结合强度。能谱分析和X射线衍射仪分析表明,涂层主要成分为Ti且与基体间的界面清晰,元素互相扩散现象不明显。送粉气体压力为5MPa、送粉温度为900℃时,所制备的钛涂层的极化电阻最大。各涂层经过1 000 h中性盐雾加速腐蚀试验后表面依旧完整,未发生明显的腐蚀,这表明涂层为基体提供了有效的腐蚀屏障,提高了钛钢复合板的耐腐蚀性能。结论 采用冷喷涂技术制备的钛涂层可有效提高钛钢复合板在海洋环境中的服役性能。     

纳米CeO2掺杂对烧结钕铁硼磁体表面Zn-Al涂层性能的影响

采用喷涂工艺在烧结钕铁硼磁体表面制备了不同纳米 CeO₂ 掺杂量的 CeO₂ / Zn-Al 复合涂层。 利用扫描电子显微镜、显微硬度仪、盐雾试验箱和电化学工作站对 CeO₂ / Zn-Al 复合涂层的微观结构、力学性能及耐腐蚀性能进行表征分析。 结果表明:CeO₂ 纳米颗粒较均匀弥散分布于 Zn-Al 涂层中,不仅能够增加 Zn-Al 涂层的硬度,而且可以提高 Zn-Al 涂层的屏蔽性能,CeO₂ / Zn-Al 复合涂层耐中性盐雾试验能力高达 720 h。 添加的 CeO₂ 颗粒能够隔绝 Zn-Al 涂层中的锌铝薄片之间的直接接触,起到绝缘作用,延长了腐蚀介质渗入钕铁硼基体的腐蚀通道。     

烧结NdFeB表面涂覆铝微粉涂层研究

研究一种用于烧结NdFeB永磁体表面防护的新型铝微粉涂层技术.用扫描电镜和X射线衍射仪分别测试了涂层的形貌和涂层在形成过程中的物相变化:用盐雾试验、极化曲线、EIS测试涂层的耐蚀性能,并对涂层的成膜和耐蚀机制进行分析.结果表明:铝微粉涂层呈层层重叠结构,对烧结NdFeB提供阴极保护,与铬氧化物的自钝化作用发生协同效应使得涂覆后的烧结钕铁硼耐盐雾腐蚀100 h.     

硅烷化处理对烧结钕铁硼永磁材料耐腐蚀性能的影响

采用环境友好的硅烷化处理技术在烧结钕铁硼磁体表面制备一层硅烷转化膜,对烧结钕铁硼磁体进行暂时性防护。采用正交试验对过程中的工艺参数进行优化。采用冷场发射扫描电子显微镜(SEM)、拉力试验机、动电位极化曲线及中性盐雾试验(NSS)对所制备的硅烷转化膜的形貌、膜/基体之间结合力以及耐腐蚀性能进行研究。结果表明:硅烷转化膜均匀的涂覆在烧结Nd Fe B磁体表面,涂层致密性高、无孔隙、裂纹等缺陷。硅烷转化膜与基体之间的膜/基结合力强度可达14.14 MPa。薄膜耐中性盐雾试验可达12 h,硅烷转化膜在固化过程中醇基之间脱水缩合反应使硅烷转化膜表面形成具有不同交联密度的区域,在Na Cl溶液中交联密度低的区域首先水解溶解是造成磁体表面硅烷转化膜腐蚀失效的主要原因。     

钢铁表面电弧喷涂耐蚀铝涂层性能的研究

使用电弧喷涂技术在经过喷砂处理的Q235钢板喷涂厚度约为200μm的纯铝涂层,使用聚氨酯清漆对涂层进行封孔处理。通过金相组织分析试验、电化学测试以及中性盐雾试验研究了涂层的耐蚀性。结果表明:喷涂涂层的结构致密、成分均匀,涂层和基体材料结合情况良好。对涂层进行封孔处理后,腐蚀速度显著下降,试样的耐蚀性得到了极大改善。对封孔涂层进行120 h的中性盐雾试验,未发现明显腐蚀痕迹,涂层的耐盐雾腐蚀性良好。     

6061铝合金表面电弧喷涂纯铝涂层的研究

采用电弧喷涂技术在6061铝合金基材表面制备纯铝涂层.利用金相显微镜、扫描电镜、X射线衍射仪对其显微组织结构、涂层形貌、腐蚀产物、孔隙率进行了分析.采用电化学试验、浸泡试验、中性盐雾试验检测了涂层在w(NaCl)=5%的溶液中的耐腐蚀性能.研究结果表明,在铝合金基材表面能够获得组织均匀致密,低孔隙率的纯铝涂层,涂层与基体为机械嵌合,涂层封孔处理后,试样的耐蚀性能有很大提高,涂层对基体无阴极保护作用.     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.