电刷镀镍／炭纳米管复合纳米镀层的结构与耐磨性能

用含碳纳米管的快速镍电刷镀液制备了镍／碳纳米管复合纳米镀层。研究了镀液中碳纳米管含量对镀层平均晶粒尺寸、显微结构、力学性能及耐磨性能的影响。结果表明：镀液中碳纳米管含量对镍刷镀层的平均晶粒尺寸和微结构有显著的影响，当镀液中碳纳米管含量为4％（质量分数）时，镀层有约16nm的最小晶粒尺寸：镀层的硬度和耐磨性与镀层的平均晶粒尺寸有非常好的对应关系：碳纳米管的弥散强化作用导致镀层晶粒细化和结构致密化，从而有效地改善了镀层的力学性能和耐磨性能。     

碳纳米管化学复合镀镍钴

采用化学镀的方法在碳纳米管的表面上镀镍、钴，得到了一维碳纳米管复合材料。研究了碳纳米管的前处理和施镀条件对化学镀的影响，并获得了性能良好的镀层。试验结果表明，对碳纳米管的氧化处理不但可以提高镀层性能，还可以提高碳纳米管施镀量。此外，对碳纳米管化学镀层热处理可以改善镀层的性质。     

碳纳米管铅锡复合减摩镀层的内应力研究

采用复合电沉积方法在紫铜片上制备碳纳米管铅锡合金复合减摩镀层;用阴极弯曲法研究了电流密度和镀液温度对碳纳米管铅锡复合镀层内应力的影响;在不同碳纳米管浓度的镀液中制备了复合镀层的试样,用X射线衍射法测定了各复合镀层的内应力.结果表明,碳纳米管铅锡合金复合镀层的内应力随电流密度的增加而升高,但随镀液温度的升高而降低.保证电流密度和镀液温度不变,碳纳米管的含量为2g/L,复合镀层的内应力降至最低;碳纳米管在镀层中的弥散分布起到了应力传递作用,减少了应力集中而产生的微裂纹.     

Ni—P—SiC复合镀层的研究

本文用板泵法以发动机缸套为应用对象研究了Ni—P—SiC复合镀屠的施镀工艺．镀层的性能。镀液的最佳配方为NiSO4·6HO250g／l，NiCl2·6H2O 40g／l，H3BO 35g／l，H3PO3 20g／l，添加剂2-3g／l，SiC(1—3μm)100g／l．工艺条件为：温度60℃，pH：2．5，电流密度5A／dm^2。镀层镀态硬度HV700-800，400℃热处理后HV1100。施镀中存在阳极钝化现象，用含S活性Ni阳极是解决问题的较佳方法。在MM-200磨损实验机上，将Ni—P镀层和Ni—P—SiC镀层作了对比，在SRN磨损实验机上将Ni-P-SiC镀层和硬Cr镀层作了比较。结果表明．Ni-P-SiC比Ni—P镀层耐磨5～10倍而与硬Cr相当。     

电沉积镍-碳钠米管复合镀层的工艺研究

利用电沉积方法制备了镍-碳纳米管复合镀层.分析了镀液中碳纳米管的悬浮量、镀液温度、pH值、阴极电流密度及搅拌速度对镀层中碳纳米管含量的影响.扫描电镜结果表明,碳纳米管能均匀地嵌镶于基体中,并且端头露出,覆盖于基体表面.     

摩擦喷射纳米Al2O3/Ni复合镀层的组织形貌及其性能研究

采用摩擦喷射电沉积工艺制备了纳米Al2O3／Ni复合镀层，考察了该镀层的表面和断面形貌，并对镀层性能进行了测试分析。研究表明，摩擦喷射纳米Al2O3／Ni复合镀层表面较为平整，镀层与基体结合紧密。一次性镀覆厚度达到1．40mm，远高于电刷镀纳米Al2O3／Ni复合镀层（0．35mm），镀层硬度达到650HV。在试验条件下，该镀层的耐磨性是摩擦喷射Ni镀层的1．44倍，是纳米Al2O3／Ni刷镀层的1．15倍，摩擦因数也低于摩擦喷射Ni镀层和电刷镀纳米Al2O3／Ni复合镀层。     

碳纳米管／锡基轴瓦合金复合减摩镀层的制备

采用复合电沉积方法在铜基轴瓦合金的表面制备碳纳米管/锡基轴瓦合金复合减摩镀层,研究了电沉积工艺参数对碳纳米管/锡基复合镀层的组织与性能的影响.结果表明,当阴极电流密度为1.5A/dm2,镀液中碳纳米管的质量浓度为2 g/L、镀液的pH值为1时,镀层生长良好,碳纳米管分布均匀.     

纳米硬度计测定电刷镀纳米颗粒复合镀层的弹性模量

采用电刷镀技术在钢基体表面制备了n-Al2O3／Ni纳米颗粒复合镀层，借助纳米硬度计的纳米压痕法测定了复合镀层的弹性模量及其分布。测试结果表明：n—Al2O3／Ni纳米颗粒复合刷镀层的杨氏模量约为200GPa；复合刷镀层中存在的气孔、裂纹等缺陷处具有较低的弹性模量，除这些缺陷微区外，复合刷镀层具有均一的弹性模量等力学性能。指出优化和严格控制复合刷镀层制备工艺、减少或消除镀层缺陷，是纳米颗粒复合刷镀层具有均匀性能、提高宏观力学性能的有效途径。     

n-Al2O3/Ni-P复合电刷镀层的组织及摩擦磨损特性

研究了镍磷基纳米Al2O3复合电刷镀层(n—Al2O3／Ni-P)的组织特征及摩擦磨损特性，并与镍磷合金刷镀层进行了比较。结果表明：n—Al2O3／Ni—P复合刷镀层表面粗糙度更小，组织有明显的细化倾向；当镀液中n—Al2O3含量为20g／L时，复合刷镀层的硬度最高，达561HV，是Ni-P镀层硬度的1．3倍，此时复合镀层的耐磨性也最好，磨损失重相比于Ni—P镀层，减少60％以上。     

纳米颗粒复合刷镀层性能研究及其强化机制探讨

制备了分别含有氧化铝、氧化硅、碳化硅、氧化钛和金刚石5种不同纳米颗粒的复合刷镀层，测试了各复合刷镀层的硬度、耐磨性、抗接触疲劳性能及高温性能，并探讨了纳米颗粒复合刷镀层的强化机制。结果表明：纳米颗粒复合刷镀层的硬度是不含纳米颗粒的快速镍刷镀层的1．5～1．7倍、耐磨性是1．6～2．5倍，抗接触疲劳寿命提高到10^6周次、可服役温度提高到400℃；纳米颗粒复合刷镀层的强化机制主要为细晶强化、弥散强化和位错强化。     

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.