电火花沉积WC-4Co复合层界面行为

采用新型电火花沉积设备,将亚微米WC-4Co陶瓷硬质合金材料沉积在铸钢材料上,制备电火花沉积合金涂层,利用SEM和XRD等技术研究沉积层与基体间的界面行为,分析沉积层的表面润湿性、物相形成机理、微观组织结构、界面元素分布、界面结合机理和显微硬度变化等。结果表明:电火花沉积技术可以在金属基体表面制造出微纳米非晶高熔点强化层。铸钢表面沉积层主要由Fe3W3C、Co3W3C、Si2W和Fe2C等相组成;沉积层与基体呈冶金结合,过渡层中出现一些柱状晶和等轴晶的组织结构,沉积层中细小的Fe2C和Si2W等硬质相颗粒弥散分布于Fe3W3C和Co3W3C沉积层上。沉积层的厚度大于20μm,沉积层的平均显微硬度为1803.2 HV,细小弥散分布的硬质相是沉积层硬度提高的主要因素。     

H13钢表面电火花沉积WC涂层

利用DZ-4000(Ⅲ)型电火花沉积/堆焊机,以WC为电极材料,采用氩气为保护气对H13钢基体进行了电火花表面强化.利用扫描电镜、能谱分析仪、X射线衍射仪和显微硬度计等对沉积层的成分、组织、硬度和表面粗糙度进行了研究.结果表明,利用电火花沉积工艺可获得组织均匀、致密,且与基体呈冶金结合的沉积层,沉积层平均厚度约60μm.沉积层主要由Fe3W3C、(CrFe)7C3和W2C等相组成.沉积层的平均显微硬度为1321.4 HV0.05,约为基体硬度的3倍.     

轧辊表面电火花沉积涂层的耐磨性

采用电火花沉积工艺,用WC陶瓷硬质合金在铸钢轧辊表面制备了一层合金涂层。采用X射线衍射仪、扫描电镜、显微硬度计等对沉积层的相结构、显微组织、显微硬度及耐磨性能进行了分析。结果表明:沉积层主要由Co3W3C、Fe3W3C、W2C、Si2W等相组成;沉积层与基体呈冶金结合,细小的硬质相弥散分布于沉积层中;沉积层的平均硬度为1915 HV0.3,约是基体硬度(352 HV0.3)的5.4倍;其室温耐磨性能比基体提高了2.1倍,高温耐磨性能比基体提高了1.9倍。室温下沉积层的主要磨损机理为磨粒磨损;高温下沉积层的主要磨损机理为粘着磨损、氧化磨损和疲劳磨损。     

电火花沉积与激光熔覆复合涂层的组织与性能

采用激光熔覆工艺和电火花沉积工艺在Q235钢上熔覆铁基合金粉末和WC陶瓷硬质合金,形成复合涂层.采用X射线衍射仪、扫描电镜、显微硬度计等对复合涂层的相结构、显微组织、显微硬度及耐磨性能进行了分析.结果表明:复合涂层主要是由Fe3W3C、Co3W3C、Si2W、W2C和(Fe0.51Mn0.46 Ni0.03)6C等相组成;复合涂层与基体呈冶金结合,复合涂层中电火花区域中细小的硬质相弥散分布于沉积层中;复合涂层的厚度为140～160 μm,其中电火花沉积区域约为40μm,激光熔覆工艺的涂层厚度为100～120 μm;电火花沉积层的硬度最高可达1262.9 HV,平均硬度为1151.6 HV,电火花沉积区域与激光熔覆区域之间的过渡区域的显微硬度为884.8 HV,激光熔覆区域的显微硬度平均值为578.3 HV;复合涂层的耐磨性较基体耐磨性提高2.3倍,强化层的磨损机理主要是磨粒磨损、粘着磨损和氧化磨损.     

35CrMo钢表面电火花沉积WC合金涂层的界面行为

以WC合金为电极,采用电火花沉积技术在35CrMo钢表面沉积WC合金强化涂层,考察了涂层的断面显微硬度,并通过金相显微镜、扫描电镜(SEM)、能谱(EDX)、X-射线衍射(XRD)等表征了强化涂层的微观结构.结果表明:涂层的表面显微硬度约为基体的2.5倍.涂层的耐磨性显著提高;涂层与基体的主要元素发生了相互扩散,所获涂层是由基体与WC合金电极发生反应的冶金结合层,涂层的主要成分是Fe7C3、Fe3W3C、Fe7C3、Fe7W6、Fe3W3C和Fe7W6.     

铸钢材料电火花表面沉积WC-4Co涂层的组织与性能

采用电火花沉积工艺,在铸钢表面制备了WC-4Co沉积涂层,采用X射线衍射仪、扫描电镜、显微硬度计等对沉积层的相结构、显微组织、显微硬度及耐磨性能进行了分析.结果表明:沉积层主要由Co3W3C、Fe3W3C、W2C、Fe7W6等相组成;沉积层与基体呈冶金结合,Fe7W6、W2C等硬质相弥散分布于沉积层中,部分区域硬质相达到了纳米颗粒尺寸;沉积层的平均硬度为1517HV0.3,约是基体硬度(502 HV0.3)的3倍;其耐磨性能比基体提高了2.4倍;沉积层的主要磨损机制为疲劳磨损,细小的弥散分布的硬质相是沉积层硬度以及耐磨性能提高的主要因素.     

不锈钢1Cr18Ni9Ti电火花沉积层的组织和成分

以YG8合金为电极,1Cr18Ni9Ti不锈钢为基体,研究了电火花沉积工艺对沉积层组织结构及沉积层性能的影响.研究结果表明,电火花沉积功率和沉积时间对电火花沉积层的厚度和硬度有一定的影响;沉积工艺影响沉积层内合金元素的分布,导致沉积层内的碳化物有明显的差异.当小功率短时间沉积时,白亮层的物相主要为Cr0.19Fe0.07Ni0.01、WC1-x、CoCx和少量的Ni-Cr-Fe;使用大功率长时间沉积时,白亮层的物相主要为(Cr Fe)7C3、CrC、Co3W3C和Ni-Cr-Fe.     

不锈钢1Cr18NigTi电火花沉积层的组织和成分

以YG8合金为电极，1Cr18Ni9Ti不锈钢为基体，研究了电火花沉积工艺对沉积层组织结构及沉积层性能的影响。研究结果表明，电火花沉积功率和沉积时间对电火花沉积层的厚度和硬度有一定的影响；沉积工艺影响沉积层内合金元素的分布，导致沉积层内的碳化物有明显的差异。当小功率短时间沉积时，白亮层的物相主要为Cr0．19Fe0．07Ni0．01、WC（1-x）、CoCx和少量的Ni-Cr-Fe；使用大功率长时间沉积时，白亮层的物相主要为（CrFe），C3、CrC、Co3W3C和Ni-Cr-Fe。     

铸钢表面电火花沉积层摩擦磨损性能

采用新型电火花沉积设备,把WC-4Co陶瓷硬质合金材料沉积在铸钢材料上,制备了电火花沉积合金涂层,用SEM、XRD等技术研究了沉积层的物相、微观组织结构、元素分布、显微硬度及室温高温耐磨性能及磨损机理。结果表明:沉积层主要由Fe3W3C、Co3W3C和Fe2C等相组成;沉积层与基体呈冶金结合,过渡层出现一些柱状晶和树枝状晶组织结构,沉积层中细小的Fe3W3C和Co3W3C等硬质相颗粒弥散分布于Fe2C基体上。沉积层的平均显微硬度为1803.2 HV;室温下沉积层的耐磨性和300℃高温条件下沉积的耐磨性分别比同样条件下铸钢材料的磨损性能提高了2.5倍和3.4倍;不论室温还是300℃高温条件下沉积层的磨损机理主要是粘着磨损、疲劳磨损、氧化磨损和磨粒磨损的综合作用,细小的弥散分布的硬质相是沉积层硬度及耐磨性提高的主要因素。     

BT20钛合金表面电火花沉积WC涂层微观组织研究

以WC为电极,氩气为保护气,采用电火花沉积方法在BT20钛合金基体上制备了强化沉积层。利用SEM、EDS和XRD分析了沉积层的微观结构和物相,利用显微硬度计测试了沉积层截面的显微硬度。结果表明,沉积层主要由TiC、WC、W和W2C相组成,TiC是电极材料与基体材料反应形成新相,是沉积层的主要组成相;沉积层与基体结合致密,形成良好的冶金结合。沉积层表面呈"泼溅状"形貌,截面组织形貌中观察到纳米级微晶堆垛结构和少量的树枝晶,反映了电火花沉积过程的快速加热和冷凝机制。沉积层显微硬度呈梯度变化,涂层最大硬度是基体的3倍。     

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。