1Cr18Ni9Ti奥氏体不锈钢的真空固溶渗氮处理

为了提高表面硬度和耐磨性,对1Cr18Ni9Ti不锈钢进行真空固溶渗氮处理。采用金相显微镜,X射线衍射仪、显微硬度计和耐磨试验机分析了渗氮层的组织与性能。结果表明,1Cr18Ni9Ti不锈钢经1 050℃真空固溶渗氮8 h后,获得了由γ′-Fe4N、CrN及含氮奥氏体组成的渗氮层;渗氮层组织致密,表面硬度为900~950 HV,有效渗层深度200μm以上;合金耐磨性得到改善,磨损失重仅为基体合金的1/26。     

R60705锆合金的表面氧化改性

对锆合金R60705在480、550、650、750℃加热保温4h进行了表面氧化处理,运用硬度测试、显微组织观察、XRD分析、阳极极化曲线的测试和均匀性腐蚀试验等方法对氧化层性能进行了研究.结果表明,R60705合金氧化层表面硬度明显高于基体硬度,最高达600 HV0.05.在650、750℃处理的氧化层的主要由单斜氧化锆ZrO2构成,对基体不具保护作用.过高处理温度会降低R60705合金的腐蚀电位、降低耐腐蚀性能.在550℃以下氧化4h形成多种结构混合的ZrO2,可以紧密覆盖基体形成保护,其氧化层各项性能均优于在650、750℃处理的氧化层.     

液压柱塞泵用30CrMoV9钢的调质与气体渗氮工艺

为提高液压柱塞泵用30CrMoV9钢的综合性能及表面的耐磨性和抗疲劳性,对30CrMoV9钢的调质工艺及粗加工后的气体渗氮工艺进行了研究,对调质硬度、渗氮层深度、渗氮后的显微组织、渗氮层硬度等进行了测试。结果表明,经900 ℃淬火及630～640 ℃的回火处理后,30CrMoV9钢可满足硬度在28~35 HRC的要求;调质态30CrMoV9钢进行气体渗氮处理后,表面平均硬度可达750 HV0.5以上,可有效提高零件的接触疲劳强度。     

TD3钛合金离子渗氮层的摩擦磨损性能

采用等离子表面渗氮技术对TD3合金进行渗氮处理,并对渗氮层显微组织、相组成及硬度进行检测。对渗氮前后TD3合金分别进行常温(25 ℃)及600 ℃的摩擦磨损试验,分析摩擦温度对其摩擦因数、磨痕形貌及磨损率的影响;结果表明,离子渗氮处理后TD3合金表面形成一定厚度的氮化物层,氮化物层在降低摩擦因数的同时,显著降低了TD3合金的磨损率,温度由25 ℃升至600 ℃时,磨痕形貌变化较大,摩擦因数及磨损率也有一定幅度的增加。     

TB8钛合金间歇式真空气体渗氮层的组织与性能

为了提高表面硬度和耐磨性,对TB8钛合金进行间歇式真空气体渗氮处理。利用XRD和SEM分析了改性层的物相组成和显微组织,并对改性层的表面硬度和耐磨性进行了研究。结果表明,TB8钛合金经800 ℃间歇式真空气体渗氮4 h后,表面改性层物相主要由TiN、TiN0.3、Ti2AlN、及α-Ti组成,渗氮层组织致密,与基体结合良好,表面硬度为900-950HV,比基体硬度提高了近3倍,硬化层厚度为80-100 μm,由于表面形成了梯度硬化层,耐磨性得到了极大改善。     

离子渗氮-渗硫对Ti-6Al-4V复合渗层组织与性能的影响

运用渗氮-渗硫复合处理技术在Ti-6Al-4V表面形成复合渗层。用X射线衍射仪、扫描电子显微镜对渗氮后600℃下不同时间渗硫所形成的复合渗层的相结构、表面及微观形貌进行了分析;并对复合渗层的截面硬度梯度进行了测定。结果表明:复合渗层由钛的硫化物、钛的氮化物、过渡层及基体组成。在渗硫温度一定时,渗硫时间的变化,会对渗层的截面硬度梯度、截面形貌产生较大的影响。其中900℃×4 h渗氮+600℃×3 h渗硫的复合处理,所得到的复合渗层是较理想的摩擦学表面。     

马氏体不锈钢不同渗氮方法对比试验

采用离子渗氮、液体渗氮及气体渗氮对耐蚀耐热马氏体型热稳定不锈钢1Cr12Ni2WMoVNb进行表面改性,研究了不同渗氮方法下不锈钢的硬度、组织形貌、物相变化及脆性,并对3种渗氮方法下不锈钢的耐蚀性及耐高温磨损性能进行了比较。结果表明:3种渗氮方法均可大幅度提高不锈钢的表面硬度,且不同渗氮处理后不锈钢的渗层组织结构大致相同,但表面物相有所差异,离子渗氮后的表面物相主要为Fe₄N及少量CrN相,液体渗氮后为Fe₃O₄及ε相,气体渗氮后为Fe₃O₄、Fe₄N及少量ε相;3种渗氮方法均可提高不锈钢的耐磨损性能,特别是在500~600 ℃下的高温耐磨性得到了大幅提升,但不锈钢渗氮后的耐蚀性均有所降低。     

TC4钛合金负压真空脉冲渗氮层的组织与性能

在氮气为负压及不同温度条件下(750、800、850和900℃)对TC4钛合金进行真空脉冲渗氮处理,采用X射线衍射,自动显微硬度测试、滑动干摩擦及电化学极化试验等手段分析了渗氮硬化层的组织与性能。结果表明:TC4钛合金渗氮处理后表面形成了一层由TiN_(0.3)、TiN、Ti_2N和AlTi_2N组成的多相化合物层;其表面硬度、渗层深度及耐磨性均随渗氮温度升高而提高。其中,850℃渗氮后合金有效硬化层深度约为30μm,硬度梯度平缓,其磨损量比原样下降1个数量级,综合性能最优。真空渗氮后合金耐蚀性均能得到大幅度改善。     

不同压力对 TC4 钛合金真空脉冲渗氮的影响

目的采用不同压力对TC4钛合金进行真空脉冲渗氮处理,提高其表面硬度及耐磨性。方法通过金相显微镜、X射线衍射仪、显微硬度计及耐磨试验机分析渗氮硬化层的组织与性能。结果 TC4钛合金经过真空气体渗氮处理后,形成了由Ti N,Ti2Al N和钛铝金属间化合物Ti3Al组成的复合改性层。渗氮压力太低,表面氮化物数量较少,氮化物层较薄;随渗氮压力的增大,表面氮化物数量增多,表面硬度及耐磨性增加。压力为0.015 MPa时,氮化物层表面硬度最大,表面硬度为1100~1200HV,有效硬化层深度为50~60μm。渗氮压力继续增加,表层组织变得疏松,表面硬度及耐磨性开始降低。结论选择合适的渗氮压力和表面氮浓度进行真空脉冲渗氮,可以提高钛合金表面硬度,改善耐磨性。     

无氢离子渗氮Ti6Al4V合金摩擦学性能的研究

以纯氮气为气源,在Ti6Al4V合金表面进行离子渗氮而形成渗氮层。对渗氮层的显微组织、相结构及显微硬度等进行了分析,并用MMW-1A摩擦磨损试验机对渗氮层的摩擦学性能进行了研究。结果表明:在纯氮气、850℃的渗氮条件下,渗氮层主要由化合物Ti N、Ti2N和α-Ti等相组成;渗氮层的硬度较基体材料有较大提高;在滑动摩擦磨损试验中,渗氮层虽无减摩效果,但其耐磨性较基材大幅提高;未渗氮处理试样的磨损机理是磨粒磨损和局部的粘着磨损,渗氮后试样的磨损机理是磨粒磨损和局部的疲劳剥落。     

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。