反应机械合金化/退火制备Al2O3/Fe3Si纳米复合粉体

以Fe2O3粉、Si粉和Al粉为原料,采用反应机械合金化/退火法制备出了Al2O3/Fe3Si纳米复合粉体。利用X射线衍射仪（XRD）和扫描电子显微镜（SEM）对复合粉体球磨以及退火过程中的固态反应过程、表面形貌进行表征。研究表明,Fe2O3-Si-Al混合粉体球磨5 h后发生反应生成Al2 O3、Fe5 Si3、Fe3 Si、FeSi,球磨20 h后生成Al2 O3/Fe3 Si,球磨20 h的粉体在900℃条件下退火1 h的组成物相未发生变化,复合粉体颗粒呈球形,其尺寸为5μm左右,分布均匀,组成相Al2O3和Fe3Si的晶粒尺寸分别为26.6 nm和28.3 nm。     

Al2O3原料种类对固相反应法合成锌铝尖晶石的影响

采用固相反应法,合成了锌铝尖晶石粉体。运用热分析、XRD、SEM分析等方法,研究了Al2O3原料种类对合成锌铝尖晶石的影响。研究表明:原料种类对合成反应开始温度有直接影响,以Al(OH)3作为Al2O3的原料与以非活性Al2O3作原料相比,生成锌铝尖晶石的开始反应温度降低近400℃;XRD和SEM分析表明,以Al(OH)3作为Al2O3的原料,锌铝尖晶石的开始生成温度为800℃,随合成反应温度升高,锌铝尖晶石的生成量显著增加;以ZnO、Al(OH)3为原料合成锌铝尖晶石的最佳合成温度为1200℃,保温时间为3h,合成得到的锌铝尖晶石呈立方晶粒,晶形发育完整,平均粒径为15μm。     

燃烧合成TiB2-Al2O3陶瓷复合粉体及其表征

采用TiB2-Al2O3-Al还原体系，通过燃烧还原技术制备了TiB2-Al2O3陶瓷复合粉体。利用XRD，XPS和SEM技术对合成粉体的相组成、化学组成及宏观组织结构进行了分析。复合粉的显微结构由TEM和HREM进行表征。结果表明，用燃烧合成法在420℃～700℃之间可制得TiB2-Al2O3陶瓷复合粉体。该粉体仅由TiB2和Al2O3两相组成，颗粒分布较均匀。由于TiB2与Al2O3间形成了结合良好的界面，颗粒间彼此能有效地抑制晶粒长大，从而使TlB2-Al2O3陶瓷复合粉的粒径减小，颗粒平均粒度在3μm～5μm之间。     

机械化学还原法快速制备Mo5Si3-Al2O3纳米复合粉体（英文）

以MoO3粉、Mo粉、Si粉及Al粉为原料,采用机械合金化法合成了纳米Mo5Si3-20%Al2O3(质量分数)复合粉体。采用XRD、SEM、TEM和DTA等对复合粉体在球磨过程中结构变化进行了研究。结果表明:球磨10h后合成的Mo5Si3-20%Al2O3复合粉体,反应以爆炸模式进行。球磨30h后,Mo5Si3和Al2O3的晶粒尺寸分别为36.3nm和21.9nm。随着球磨时间的延长,Mo5Si3和Al2O3的晶粒尺寸变小,衍射峰宽化程度降低。DTA和XRD分析结果表明,复合粉体具有好的热稳定性,球磨30h后再在1000℃退火1h后复合粉体没有发生物相转变。     

TiN-SiC复合陶瓷材料的研制

以Ti、Si3N4、石墨和α-SiC粉体为原料,通过反应热压合成了TiN-SiC复合陶瓷材料。研究结果表明:在TiN-SiC复合陶瓷材料中,TiN和SiC晶粒细小均匀,无异常晶粒长大现象,TiN晶粒尺寸为1μm～7μm,SiC均匀分布于TiN之间;该复合材料的密度、维氏硬度和断裂韧性分别为4.41g/cm3、13.6GPa和6.89MPa·m1/2,其增韧机制主要为裂纹偏转和裂纹分叉机制。     

Al-TiO_2-B_2O_3反应体系的机械力化学与热化学行为

通过机械球磨系统地研究Al-TiO2-B2O3反应体系粉体的机械力化学与热化学行为。结果表明:Al-TiO2-B2O3复合粉体球磨20h后,中位径可达到4.35μm,形状近乎球形,并生成少量Al2O3、TiB2等新相;机械力化学作用使其在400℃左右就可发生缓慢的固相反应,在670℃时反应最为剧烈;在700℃热处理时,产物大部分为Al2O3和TiB2;在1000℃热处理时,产物全部为Al2O3和TiB2。     

反应等离子喷涂合成Fe-FeAl2O4-Al2O3复合涂层的研究

利用机械团聚法制备了适合等离子喷涂的Fe2O3／Al复合粉体，将此粉体送入等离子焰流，通过复合粉的自反应制备含有Fe、Al2O3和FeAl2O4的复合陶瓷涂层。利用扫描电镜（SEM）、X射线衍射仪（XRD）和透射电镜（TEM）等检测手段对反应等离子制备的复合涂层进行了研究。结果表明：涂层具有以层状陶瓷为骨架，球形金属为弥散相的组织，反应生成涂层的过程是分步进行的，由于反应生成的部分纳米颗粒以及金属的存在，使得涂层的耐磨性和韧性比普通Al2O3涂层有了较大的提高，尤其在高载荷作用下，复合涂层的耐磨性比普通Al2O3提高近两倍。     

挤压铸造颗粒增强铝基复合材料的凝固组织

用Al-ZrOCl2组元通过熔体直接反应法原位合成了Al3Zr和Al2O3颗粒增强铝基复合材料，在720℃时进行常规浇注和挤压成形试验，SEM观察凝固组织显示挤压试样晶粒细小，没有明显的缩孔疏松等浇注缺陷，因为挤压铸造是在高压下的结晶凝固和塑性变形，是强制补缩一密实两过程的复合，外加压力提供的膨胀能增加了形核率，这有利于提高复合材料的综合力学性能和耐磨性。     

高钛渣碳热还原氮化合成TiN/O′-Sialon导电陶瓷粉体

以高钛渣、硅灰和高铝矾土熟料为原料,采用碳热还原氮化法合成TiN/O′-Sialon导电陶瓷粉体。利用XRD、SEM和EDS检测手段研究合成温度及恒温时间对粉体相组成和显微形貌的影响,并探讨合成机理。结果表明:随合成温度的升高和恒温时间的延长,产物中O′-Sialon的含量逐渐增加,并在1 375~1 400℃、恒温7 h时成为产物主晶相,此时产物中还有较多TiN和少量β′-Sialon生成。继续提高温度和延长反应时间,体系气氛的改变导致O′-Sialon迅速向β′-Sialon转化。合成粉体中O′-Sialon晶粒多呈等轴状,粒度约2μm,TiN晶粒为细小粒状。此外,反应体系中还有大量白色β′-Sialon晶须状沉积物生成。     

自蔓延高温合成TiB2／Al2O3复合材料的力学性能

以普通商用TiO2为原料，与铝粉、碳化硼进行自蔓延（SHS）高温合成TiB2／Al2O3复合材料，通过差热和X射线衍射分析，确定了TiO2、Al及B4C的反应机制，得到了生成TiB2／Al2O3复合粉体的最佳工艺条件。测定了TiB2／Al2O3复合粉体相关的力学性能，得到材料的抗压强度为87．2MPa，抗弯曲强度为104．3MPa。SEM观察发现生成相中存在大量的气相或气孔，生成物微观区域不太均匀，材料的断裂形式主要为脆性断裂，生成物的颗粒尺寸为亚微米级。     

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。