Ti＿3Al基合金中α_2／α_2＋β相界的计算与测定

对Ｔｉ_３－Ｍｏ－Ｎｂ，Ｔｉ_３Ａｌ－Ｎｂ－Ｖ，Ｔｉ_３Ａｌ－Ｚｒ－Ｖ三个赝三无合金系的实验结果表明，α_２／α_２＋β相界遵守电子浓度规律，且合金元素的价电子数由它们的电子结构决定过渡族元素Ｔｉ，Ｚｒ．Ｖ，Ｍｏ，Ｎｂ的价电子为ｓ＋ｄ电子。即Ｎ_（Ｔｉ）＝Ｎ_（Ｚｒ）＝４（ｓ~２ｄ~２），Ｎ_ｖ＝５（ｓ~２ｄ~３），Ｎ_（Ｎｂ）＝５（ｓ~１ｄ~４），Ｎ_（Ｍｏ）＝６（ｓ~１ｄ~５）、非过渡族元素Ａｌ的价电子为ｓ＋ｐ电子，即Ｎ_（Ａｌ）＝３（ｓ~２ｐ~１）α_２相的计算模型为Ｎ＝ΣＮ_ｉｆ_ｉ，α_２／α_２＋β相界的特征电子浓度值为Ｎ_ｃ＝ΣＮ_ｉｆ_ｉ＝３．７８７．     

TiAl基合金的制备

在Ｔｉ—Ａｌ系金属间化合物中，ＴｉＡｌ基合金是最有商业竞争力的，具有在下个十年推动结构材料变革的潜力［１］．同时，作为减重材料来代替镍基超合金，已经应用在喷气式发动机和一些非航空用结构件上，如汽车发动机叶片等．由于双相区微观结构控制能力的提高和它们显示出的更多优异性能，当前研究［１－４］的重点一般放在具有少量第二相（ａ２相和有序相）的近ＴｉＡｌ基合金上，近－ＴｉＡｌ基合金铝含量固定在４５％－４８％（原子分数）Ａｌ上，一般含有０．１％～２．５％第二相元素，如Ｎｂ、Ｃｒ、Ｔａ、Ｗ、Ｍｎ、Ｍｏ等元素．…     

THE CALCULATION AND DETERMINATION FOR α_2 PHASE AND α_2/α_2+βPHASE BOUNDARY IN Ti_3AI BASED ALLOYS

对Ｔｉ_３－Ｍｏ－Ｎｂ，Ｔｉ_３Ａｌ－Ｎｂ－Ｖ，Ｔｉ_３Ａｌ－Ｚｒ－Ｖ三个赝三无合金系的实验结果表明，α_２／α_２＋β相界遵守电子浓度规律，且合金元素的价电子数由它们的电子结构决定过渡族元素Ｔｉ，Ｚｒ．Ｖ，Ｍｏ，Ｎｂ的价电子为ｓ＋ｄ电子。即Ｎ_（Ｔｉ）＝Ｎ_（Ｚｒ）＝４（ｓ~２ｄ~２），Ｎ_ｖ＝５（ｓ~２ｄ~３），Ｎ_（Ｎｂ）＝５（ｓ~１ｄ~４），Ｎ_（Ｍｏ）＝６（ｓ~１ｄ~５）、非过渡族元素Ａｌ的价电子为ｓ＋ｐ电子，即Ｎ_（Ａｌ）＝３（ｓ~２ｐ~１）α_２相的计算模型为Ｎ＝ΣＮ_ｉｆ_ｉ，α_２／α_２＋β相界的特征电子浓度值为Ｎ_ｃ＝ΣＮ_ｉｆ_ｉ＝３．７８７．     

用X射线能谱研究金基六元合金

利用Ｘ射线能谱（ＥＤＳ）和透射电子显微术（ＴＥＭ）等手段研究了Ａｕ－Ｎｉ－Ｆｅ－Ｃｒ－Ｉｎ－Ｚｒ合金的显微组织。研究结果表明，合金主要由Ａｕ基固溶体和Ｎｉ基固溶体组成。此外还有两种第二相粒子，一种粒子（命名为η相）含Ｃｒ量为９０ａｔ％，属简单正交结构，ａ＝０．４４８ｎｍ，ｂ＝１．４０ｎｍ，ｃ＝１．２１ｎｍ；另一种粒子为具有ｆｃｃ结构的化合物（Ｎｉ，Ａｕ）＿５Ｚｒ，ａ＝０．６８２ｎｍ。     

TiC及Ti2C在铝结晶过程中的核心作用

将工业纯铝（９９．７％）用亚包晶成分的Ｔｉ（＜０．１５％）实行变质处理，采用电子衍射等方法研究其结晶核心，证明α－Ａｌ核心除ＴｉＣ粒子外，还存在Ｔｉ_２Ｃ。ＴｉＣ为立方晶格，ａ＝０．４３８０ｎｍ；Ｔｉ_２Ｃ为正交晶格，ａ＝１．２０ｎｍ，ｂ＝１．０６ｎｍ，ｃ＝１．５０ｎｍ     

用机械合金化方法制备Ni-Al系金属间化合物

用球磨机分别对Ｎｉ－５０ａｔ．－％Ａｌ和Ｎｉ－２５ａｔ．－％Ａｌ混合粉末进行机械合金化，并对Ｎｉ_３Ａｌ预合金粉末进行高能球磨，观察了粉末的金相组织，测定了粉末的硬度、平均直径和晶粒尺寸，并作了ＸＲＤ物相分析结果表明，经３ｈ研磨，Ｎｉ－５０ａｔ．－％Ａｌ混合粉末变成ＮｉＡｌ金属间化合物，其晶粒直径约５ｎｍ；经５ｈ机械球磨，Ｎｉ－２５ａｔ．－％Ａｌ混合粉末成为无序的亚稳定Ｎｉ固溶体，而Ｎｉ_３Ａｌ预合金粉末由Ｌｌ_２型长程有序金属间化合物转变为ｆｃｃ无序固溶体；球磨更长时间，则形成纳米晶．     

两种Ti3Al在水中的低频疲劳研究

研究了Ｔｉ３Ａｌ和Ｔｉ３Ａｌ＋Ｎｂ两种金属间化合物在空气和蒸馏水中的低频（０．５Ｈｚ）疲劳行为。结果表明，水介质能降低这两种材料的腐劳抗力。随应力比增加，腐蚀疲劳裂纹扩展速率亦增加，Ｋｍａｘ是该材料－介质体系的力学控制因子。Ｔｉ３Ａｌ＋Ｎｂ的腐蚀疲劳抗力高于Ｔｉ３Ａｌ。断口分析显示发生了沿α２相内滑移面的解理开裂（Ｒ＝０．１）或沿α２／β相界的相间开裂（Ｒ＝０．５）。     

氯化法生产四氯化钛中泥浆的回收处理

用机械合金化工艺制备了Ａｌ－１２Ｔｉ－６Ｎｂ合金，对其物相组成和显微组织进行了ＸＲＤ、电子探针和金相分析与观察，测试了其室温力学性能，并用ＳＥＭ观察了断口形貌，结果表明：ＭＡ Ａｌ－１２Ｔｉ－６Ｎｂ合金中生成了粗细不均的Ａｌ３Ｔｉ金属间化合物粒子，但未形成Ａｌ３Ｎｂ；在较大的Ａｌ３Ｔｉ颗粒和Ｎｂ趋向于平行热压面分布。Ｎｂ的加入使合金较好地发挥了大个Ａｌ３Ｔｉ和盘状Ｎｂ颗粒的协同补强增韧作用，三点弯     

Ti－24Al－14Nb－3V－0．5Mo合金的超塑性

研究了温度及应变速率对Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ－０．５Ｍｏ（ａｔ．－％）合金超塑性能的影响．试验结果表明，在９８０℃，３．５×１０~（－４）ｓ~（－１）的最佳超塑变形条件下，合金显示出较高的超塑性；应变速率敏感性指数ｍ为０．６９，拉伸延伸率Ｅｌ．为８１８％．根据其细小的α_２＋β_０两相组织和等温拉伸的试验方法，确定合金的超塑性属于细晶组织超塑性．在超塑变形过程中，合金无空洞产生，显微组织发生动态粗化．     

Ti_3Al＋Nb在甲醇中沿相界的应力腐蚀SCIEI

研究了Ｔｉ－２４Ａｌ－ｌｌＮｂ合金中Ｔｉ３Ａｌ＋Ｎｂ金属间化合物在甲醇溶液中的应力腐蚀及室温氢致开裂的规律，探讨了组织结构的影响．结果表明，Ｔｉ３Ａｌ＋Ｎｂ在甲醇溶液中应力腐蚀敏感性很高，不向组织应力腐蚀断裂归一化门槛值为而ｋ（ＩＳＣＣ）／ＫＣ＝０．５３－０．６９；应力腐蚀裂纹止裂门槛值为Ｋ（ＩＳＣＣ）／Ｋ（ｌｉ）＝０．６１－０．７９．Ｔｉ３Ａｌ＋Ｎｂ在室温动态充氢时能发生氢致开裂，门槛值和应力腐蚀相近，但裂纹扩展速率或断裂时间比应力腐蚀要慢１－３个数量级．两者断口形貌也不相同．发现了相界应力腐蚀现象．对固溶后炉冷试样，当ＫＩ较低时，应力腐蚀裂纹优先沿α２／β相界形核和扩展，从而获得相界应力腐蚀断口．如固溶后空冷或ＫＩ较高，则不出现相界应力腐蚀．     

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。