熔体旋淬Ml（NiCoMnAl）5贮氢合金的微结构与电化学行为

研究了熔体旋淬和常规熔铸Ml(NiCoMnAl)5贮氢合金的微结构和电化学行为。SEM和XRD分析表明,熔体旋淬合金由细小的柱状晶组成,它们的晶体结构与铸态一样,都为CaCu5型六方晶休结构。电化学测试表明,旋淬态合金电极初始容量较高（＞210mA.h/g)经1－2次循环就可达到最大放电容量。旋淬速度为10m/s的合金电极的放电容量（294mA.h/g)稍高于铸态合金电极的容量。所有旋淬态合金电极充放电循环稳定性皆优于铸态合金,在600mA/g电流质量密度下,旋流速度为10m/s的合金电极具有较好的高倍率充放电能力,但随着循环次数的增加,其容量稳定性稍次于旋淬速度为25m/s和40m/s的合金电极。     

热处理对低Co贮氢合金Ml(NiCoMnAlFe)_5电化学性能的影响

系统研究了热处理对低Co贮氢电极合金Ml(NiCoMnAlFe) 5 电化学性能的影响。结果表明 ,铸态合金的放电容量为 2 97mA·h/g ,经 2 68次充放电循环后的容量保持率为 68% ;经热处理后 ,合金的放电容量提高至30 2mA·h/g ,2 68次充放电循环后的容量保持率提高至 80 % ,热处理提高了合金的放电容量和循环稳定性 ;同时发现热处理会导致合金高倍率放电特性的恶化。XRD测试表明 ,热处理降低了晶格应力与晶格缺陷 ,改善了合金的成分均匀性 ,从而提高了合金的放电容量和循环稳定性。     

Improved Cycle Stability of La0.75-xPrxMg0.25Ni3.2Co0.2Al0.1 (x=0-0.4) Electrode Alloys by Melt Spinning

为了改善 La-Mg-Ni 系 A2B7型电极合金的电化学循环稳定性,用 Pr 部分替代合金中的 La,并用熔体快淬工艺制备了La0.75-xPrxMg0.25Ni3.2Co0.2Al0.1(x = 0, 0.1, 0.2, 0.3, 0.4)电极合金。用 XRD、SEM、TEM 分析了铸态及快淬态合金的微观结构。结果表明,铸态及快淬态合金均具有多相结构,包括 2 个主相(La,Mg)Ni3及 LaNi5和 1 个残余相 LaNi2。熔体快淬导致 LaNi5相增加而(La,Mg)Ni3相减少。电化学测试结果表明,熔体快淬显著地提高合金的电化学循环稳定性。当淬速从 0 m/s (铸态被定义为淬速 0 m/s)增加到 20 m/s 时,x=0 合金 100 次充放循环后的容量保持率从 65.32%增加到 73.97%,x=0.4 合金的容量保持率从 79.36%增加到 93.08%。     

铸态和快淬态Mm(NiCoMnAl)5合金的电化学性能及相结构

本文研究了铸态和快淬态MmNi3．7Co0．6Mn0．4Al0.3贮氢合金的电化学性能和相结构。电化学测试结果表明：快淬态合金的活化性能比铸态合金差，淬速为10m／s和16m／s的快淬态合金的最大放电容量高于铸态合金，放电电压平台更为平坦。淬速为22m／s和28m／s的快淬态合金的最大放电容量低于铸态合金。随着淬速的增加，合金电极的循环稳定性提高。X射线衍射结果表明：铸态和快淬态合金均由CaCu5型主相和一个第二相组成，快淬使得第二相衍射峰减弱。合金成分更为均匀。快淬态合金的晶格参数大于铸态合金。晶格参数的增加是快淬合金具有良好循环稳定性的一个重要原因。     

A组分变化对AB2型储氢合金组织结构及电化学性能的影响

设计了两种成分AB2型合金,（Zr1-XTiX）（NiVMnCo）2＋α,采用XRD、SEM、TEM以及电化学性能测试方法分别对它们的铸态、快淬态及快淬态经过773 K、973 K和1 173 K退火处理的合金进行研究,结果表明,在AB2型储氢合金中加入少量Ti,可以增加电极的放电容量,提高循环寿命。熔体旋转快淬制备的非晶态合金电极的电化学性能差。快淬样品经过退火后,可获得纳米晶结构,能够大幅度提高电极材料的放电容量（370 mAh/g）和循环寿命（300次循环后容量衰减3%）。     

快淬对低钴贮氢合金的电化学性能影响

为改善低钴贮氢合金的综合电化学性能,对其进行不同速度的快淬处理.结果表明:合适的快淬速度不仅可以大幅度的提高放电容量,而且明显的改善合金的循环稳定性和放电电压特性.18 m/s快淬低钴合金具有较好的综合电化学性能.但快淬使得合金的活化性能有所降低.利用X射线衍射、扫描电镜对铸态及快淬合金进行微观分析,讨论了快淬对低钴贮氢合金电化学性能的影响机理.     

快淬对低钴贮氢合金的电化学性能影响

为改善低钴贮氢合金的综合电化学性能,对其进行不同速度的快淬处理。结果表明,合适的快淬速度不仅可以大幅度的提高放电容量,而且明显的改善合金的循环稳定性和放电电压特性。18 m/s快淬低钴合金具有较好的综合电化学性能,但快淬使合金的活化性能有所降低。利用X射线、扫描电镜对铸态及快淬合金进行微观分析。分析了快淬对低钴贮氢合金电化学性能的影响机理。     

快淬AB5型贮氢合金研究

使用快淬工艺制备了两种成分的ＡＢ５型贮氢合金并做了电化学充放电循环实验,比较了它们的起始活化性能、放电容量、电化学循环稳定性、放电电压性能等。发现快淬合金的电化学循环稳定性明显优于铸态合金,放电电压平台性能也较好,但快淬导致起始活化速度慢,放电容量也有所降低。快淬对放电电压平台高低的影响随合金成分的不同而改变     

快速凝固非化学计量比储氢合金LaNi4.75Mn1.25 晶体结构和电化学性能

采用熔体快淬方法得到了无Co过化学计量比合金La(NiMn)6的非平衡亚稳单相CaCu5型结构,分析和研究了合金非平衡组织结构和电化学吸放氢性能.x-ray衍射分析表明,快速凝固合金组织为CaCu5型结构单相组织,与常规熔铸合金比较,快速凝固合金的晶胞参数发生了明显的各向异性变化:随着冷却速度增加,CaCu5型晶胞a轴减小,c轴及轴比c/a增大.电化学实验研究表明,当合金快凝速度≥20m/s时,过化学计量比La(NiMn)6合金MH电极的循环稳定性得到不同程度的改善,快凝速度≥30m/s时,合金电极具有良好的循环稳定性,其最大电化学容量为256mAh/g～277mAh/g,循环100次后合金MH电极容量保持率为63%～97.8%.快速凝固合金均大大提高了合金的电化学稳定性,但随着冷却速度增加其活化性能和电极容量有所下降.     

制备工艺对AB5型高容量贮氢合金电化学性能的影响

研究了快淬、热处理、快淬+热处理制备工艺对铸态(LaCe)1.0(NiCoMnAl)5.0高容量贮氢合金电化学性能的影响。XRD分析表明所有合金均为单相CaCu5型结构,快淬+热处理合金相的成分和结构的均匀性最好。电化学测试结果表明,与铸态合金相比,热处理合金的放电容量和循环性能有所提高,但其倍率性能明显降低;快淬合金的活化性能、放电容量、倍率性能以及循环性能均降低;快淬+热处理合金综合电化学性能最好,具有较好的活化性能、最大的放电容量(344.7mA/g)、最大容量保持率(S100,85.67%)以及较好的倍率性能。     

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。