表面改质及强化技术

激光熔覆原位合成Cop/Cu复合涂层;铸铁等离子熔覆铁基合金耐磨涂层;电火花振动沉积TiC功能涂层的显微组;钛合金表面反应电火花沉积Ti（CN）涂层研究;高频感应熔覆WC增强Ni60合金涂层性能研究     

表面改质及强化技术

激光熔覆原位合成Cop/Cu复合涂层;铸铁等离子熔覆铁基合金耐磨涂层;电火花振动沉积TiC功能涂层的显微组;钛合金表面反应电火花沉积Ti（CN）涂层研究;高频感应熔覆WC增强Ni60合金涂层性能研究     

激光熔覆反应合成Cu-TiB2复合材料的工艺与组织研究

应用500W Nd:YAG固体激光器在纯铜表面原位合成了Cu-TiB2复合涂层.用XRD和SEM分析了熔覆层的组织和结合界面,研究了激光工艺参数对熔覆层组织的影响.实验得出了用Cu、Ti和B4C混合粉激光熔覆铜表面的优化工艺参数.结果表明,涂层与铜基体呈冶金结合,熔覆层中的TiB2颗粒细小均匀,颗粒尺寸约为300～500nm,形状接近球形.     

激光原位制备复合碳化物颗粒增强铁基复合涂层及其耐磨性的研究

通过在高碳当量铁基熔覆粉末中复合添加多种强碳化物形成元素,激光原位制备的颗粒增强铁基复合材料涂层具有颗粒析出密度大、尺寸分布均匀的优点.通过在铁基熔覆粉末中单独添加Ti,复合添加Ti+Zr以及Ti+Zr+WC的方式,运用激光熔覆技术在中碳钢表面制备了颗粒增强铁基复合涂层.用X射线衍射仪、扫描电镜和透射镜等手段研究了涂层的显微组织、颗粒相结构及颗粒相与熔覆层基体相之间的界面.通过环块磨损实验,对比渗碳淬火工艺研究了颗粒增强涂层的耐磨性能,并对磨损机制进行了讨论.结果表明,涂层微观结构是典型的亚共晶介稳组织,原位合成的颗粒是一种复合碳化物,界面处结合牢固.激光原位制备复合碳化物颗粒增强铁基复合涂层具有优异的耐磨性能.     

La2O3含量对激光熔覆TiB/Ti涂层显微结构的影响

目的 改善钛合金表面激光熔覆复合涂层的组织结构,提高钛合金的硬度,使其在相应领域得到更广泛的应用.方法 采用激光熔覆快速非平衡合成方法 制备原位反应合成L2O3-TiB增强钛基复合涂层.用L2O3、Ti和B的混合粉末在Ti-6Al-4V基体表面激光熔覆制备L2O3-TiB/Ti复合涂层,并对其进行XRD物相分析、SEM显微结构观察及显微硬度分析.结果 添加不同含量的L2O3的激光熔覆钛合金复合涂层均与基体较好的结合,涂层中均只有α-Ti和TiB两种物相.随L2O3含量的增加,激光熔覆复合涂层中的增强相TiB的形貌越均匀细小,添加不同含量的L2O3的激光熔覆复合涂层的硬度值约为基体材料的2~3倍,添加质量分数为3%的L2O3的激光熔覆复合涂层硬度最高,其显微硬度值大约为1300HV.结论 添加稀土氧化物L2O3后制备的激光熔覆钛合金复合涂层与基体结合良好,稀土元素的添加使涂层组织细化,硬度得到了明显提高.     

铜合金表面激光改性研究

利用500WYAG固体激光器在紫铜表面原位合成TiB2/Cu复合涂层,用扫描电镜分析了复合涂层的组织形貌以及熔覆层和基底之间的结合界面,测试了复合涂层的显微硬度和磨损性能。结果表明,采用激光熔覆表面改性技术可在紫铜表面合成厚度为100μm的TiB2/Cu复合涂层;涂层与铜基底形成了较好的冶金结合;TiB2分布均匀、颗粒细小,颗粒尺寸约为300～500nm;熔覆层显微硬度最高达380HV,平均硬度约240HV,是铜基底的3～4倍;TiB2/Cu复合涂层耐磨性能为紫铜的5～8倍。     

铝合金表面MoSi2/SiC复合涂层的激光熔覆制备

利用激光熔覆技术在铝合金表面制备MoSi2/SiCp复合涂层,对涂层的微观组织形成规律及其主要工艺参数对涂层组织和性能的影响进行了研究.实验结果表明,对试样进行搭接预热和在熔覆粉末中添加助熔剂CaF2是提高熔覆层质量的主要途径.采用多道搭接预热熔覆工艺和预置涂层法可以在铝合金表面获得具有完全冶金结合的原位自生SiC颗粒增韧的硅化钼陶瓷复合涂层,涂层组织主要由Mo(Si,Al)2、SiC、α-Al、Mo5Si3等相组成.熔覆层显微硬度较基体材料的显微硬度有大幅度提高,涂层显微硬度最大可达850HV0.2.     

6061铝合金激光熔覆铜基复合涂层组织及磨损性能

利用激光熔覆工艺在6061合金表面熔覆铜基复合涂层,分析熔覆涂层的微观组织及化学成分,考察熔覆合金成分变化对涂层质量、硬度以及磨损性能的影响.结果表明,熔覆层主要由(Cu,Ni)固溶体、Cu9Al4、AlFe0.23Ni0.77以及CoFe增强相等组成.优化成分条件下,Fe含量为7%,Co含量为9%,熔覆层硬质颗粒体积分数增大,大量硬质颗粒增强体弥散分布在熔覆层Cu-Ni固溶体合金基体组织中,大大增强了基体的抗磨损性能.激光熔覆后的熔覆层表面硬度比6061铝合金提高了4.5倍;磨损体积约为铝合金基线的30%,摩擦因数降至0.3002.     

激光熔覆颗粒增强金属基复合材料涂层强化机制

选用优化的激光工艺参数,利用激光熔覆工艺在中碳钢表面原位合成硬质陶瓷颗粒增强金属基复合材料涂层,涂层熔覆质量良好。涂层是由粘结金属基体和弥散分布于其中的稳定和亚稳定硬质颗粒增强相组成。激光熔覆涂层相对于中碳钢基体强化效果显著。对熔覆涂层的显微分析表明：涂层中存在细晶强化、硬质颗粒弥散强化、固溶强化和位错堆积强化等强化机制。     

Al-TiO2-C系激光熔覆制备TiC/Fe复合涂层及其组织与性能

采用激光熔覆技术,在Q235钢表面原位合成了TiC/Fe复合涂层,利用光学显微镜、XRD、SEM、EDS和显微硬度计对熔覆层的组织和性能进行了分析.结果表明:涂层组织致密,无裂纹和气孔,与基体之间呈良好的冶金结合;在激光束的加热作用下,A1-TiO2-C体系能在铁基熔池中反应并合成细小且弥散分布的TiC颗粒;熔覆层的平...     

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。