Fe73.5 Cu1 Nb3 Si13.5 B9机械合金化纳米晶粉末的特种烧结及磁性能

研究了放电等离子烧结和高压烧结工艺条件对MA Fe73.5Cu1Nb3Si13.5B9纳米晶粉末的烧结块体合金的组织结构与磁性能的影响.结果表明:球磨70 h后,获得了单相a-Fe纳米晶(约9.5 rm)过饱和固溶体粉末;DSC升温曲线中,出现4个不同强度的放热峰,依次发生了纳米晶过饱和固溶体的结构弛豫、非晶晶化以及过饱和固溶体相析出等过程,且相析出过程分两个阶段完成;在p=30 MPa,t=5 min放电等离子烧结(SPS)条件下,当温度达到1 050℃后,可获得相对密度为98.9%、主相为α-Fe的纳米晶(100nm)块体合金,其中,B3=1.34 T,Hc=7.34 kA/m,在p=5.5 GPa,t=5 min条件下,当Pw=1 150 W后,可获得相对密度约99.1%、单相α-Fe纳米晶(21.4 nm)块体合金,其中,Bs=1.14 T,Hc=8.22 kA/m.     

高压下Fe84Nb7B9纳米晶软磁块体合金的形成

采用机械合金化(MA)以及低温高压烧结工艺制备了Fe84Nb7B9软磁合金粉末及其块体合金,并利用XRD、DSC、SEM对MA合金粉末和块体合金的相结构、晶粒大小以及组织的热稳定性进行了研究.结果表明:经过15h MA后,可获得单相bcc结构的粒径小于10nm的纳米晶过饱和固溶体粉末; 在常压状态下,单相纳米晶过饱和固溶体合金在温度小于550℃时具有良好的组织热稳定性,温度小于770℃时具有良好的相热稳定性; 在p=5.5GPa,t=3min条件下,当Pw≥820W时,可获得相对密度大于98.4%、单相bcc结构的纳米晶(粒径小于10nm)块体合金.     

MA Fe-(Nb,Ti)-B纳米晶粉末热压烧结及磁性能

研究了MA法和热压烧结工艺制备的Fe84Nb7B9和Fe80Ti8B12合金粉末的产物及其块体合金的微观组织结构和磁性能。结果表明：(1)20hMA后，Fe84Nb7B9和Fe80Ti8B12均形成了单相bcc米晶过饱和固溶体，相对前者，后者纳米晶组织热稳定性明显提高，过饱和固溶体相分解温度略有降低；(2)在30MPa／900℃／0．5h热压条件下，Fe84Nb7B9和Fe80T8B12块体合金相对密度分别为96．7％和95．5％，相对前者(多相组织)，后者由超细晶(50～200mm单相α-e组成；(3)Fe80TiB12块体合金软磁性能(σ8=198．6emu／g，Hc=54．6Oe)明显高于Fe84Nb7B9块体合金(σ8=162．9emu／g，Hc=105．1Oe)，此与纳米晶粉末在热压烧结过程中所形成相的种类和晶粒尺寸大小有关。     

Fe86Zr5Nb6B3非晶合金超高压烧结

借助XRD，DSC，TEM等分析手段，研究了Fe86Zr5Nb6B3快淬带球磨粉末的热稳定性以及高压烧结条件对块体合金的相组成和晶粒尺寸的影响。结果表明：（1）球磨快淬粉末仍为非晶态，其晶化温度约510℃，该晶化过程的表观激活能庐219．5kJ／mol：（2）在5．5GPa，3min烧结条件下，当Pw=1150W后，获得了相对密度为99．1％，单相α-Fe纳米晶（20．6rim）块体合金：（3）在5．5GPa，1150W烧结条件下，当t延长至25min后，α-Fe相纳米晶粒尺寸长大到28.7nm；（4）在5．5GPa，1150W，5min烧结条件下，纳米晶块体合金的饱和磁感应强度Bs=1．26T，矫顽力Hc=4．27kA．m^-1。     

高压下Fe78Si9B13纳米晶块体合金的制备

借助XRD、DTA等分析手段,研究了快淬Fe78Si9B13非晶带的热稳定性,分析了高压烧结条件对球磨非晶粉末烧结获得的块体合金相对密度和晶粒尺寸的影响。结果表明：该非晶合金中,a—Fe相初始晶化温度为469℃,Fe2B第二相初始析出温度为509℃;在P=5．5GPa高压烧结条件下,随着烧结功率Pw的增加,块体合金的a-Fe相晶粒尺寸D逐渐增大,在10．3～14．2nm之间;块体合金的相对密度也随烧结功率Pw升高而增大,当Pw=1207W时,获得了相对密度为99．6％的a—Fe单相纳米晶块体合金,其饱和磁化强度Js=1．52T,矫顽力Hc=1．9kA／m。     

机械合金化及真空热压制备纳米晶Fe3Al的组织及性能

采用机械合金化(MA)及热压烧结工艺制备纳米晶Fe3Al块体材料。采用X射线衍射、透射电镜、扫描电镜等对MA粉体及热压块体的相及显微组织进行分析,并对热压块体的力学性能及断口形貌进行了测试分析。结果表明:Fe72Al28混合粉在球磨过程中,Al逐渐溶入Fe中,形成Fe(Al)过饱和固溶体,纳米晶粉体的结构有序度较低。在1200℃,保温1h下真空热压烧结,Fe(Al)转变为有序的DO3-Fe3Al,同时发生晶粒长大。Fe3Al块体晶粒尺寸为40.1nm,相对密度大于96%,维氏硬度626.8 HV,三点弯曲强度985MPa;弯曲断口为脆性断口,但也呈现出一定韧性断裂特征。     

90W-7Ni-3Fe纳米晶粉末的瞬时液相强化烧结特征

采用机械合金化(MA)制备了晶粒尺寸为8～18 nm的90W-7Ni-3Fe纳米晶粉末(MA粉末).将粉末注射成形,在1 480～1 500℃经3～5 min瞬时液相烧结.结果表明,采用瞬时液相强化烧结可以得到W晶粒为3～8 μm近全致密的细晶钨合金,显微组织为细小的球形W晶粒均匀地连续分布在纤维状粘结相中,烧结坯具有好的拉抻性能.长时间的传统液相烧结使球状W晶粒迅速粗化,而且密度和强度下降,但延伸率反而增加.在MA粉末中添加微量Y2O3后采用瞬时液相烧结,可以使合金抗拉强度提高到1 055 MPa,延伸率提高到16.5%.     

CoSb3纳米晶块体热电材料的制备研究

采用机械合金化．放电等离子烧结工艺(MA-SPS)，在200℃～600℃之间制备了纳米晶CoSb3合金块体材料。采用XRD和TEM对材料的相组成和微观组织进行了测试分析。实验结果表明，烧结前粉末为高能球磨得到的平均晶粒尺寸为20nm～35nm的纳米晶CoSb3粉末，SPS烧结后CoSb3合金块体的平均晶粒尺寸小于100nm，其致密度达到了91．3％～99．6％。CoSb3块体的晶粒尺寸随着烧结温度的降低而减小，而密度却随着烧结温度的升高而增加。CoSb3纳米晶块体热电材料的制备机理是MA使粉末晶粒细化到纳米级，放电等离子烧结的快速、短时、低温和特殊烧结机理显著抑制了烧结时的晶粒长大。     

纳米晶Mo-Cu复合粉末烧结行为的研究

采用溶胶-喷雾干燥-煅烧-氢气还原的方法制备了纳米晶Mo-18Cu、Mo-30Cu、Mo-40Cu复合粉末,研究了纳米晶Mo-Cu粉末的烧结行为以及Cu含量对致密化的影响.结果表明,纳米晶Mo-Cu复合粉末致密化程度高,速度快,在1050～1200 ℃烧结,Mo-30Cu和Mo-40Cu的相对密度可达98%以上,且合金晶粒细小,而Mo-18Cu在1350 ℃以上烧结,相对密度也可达98%以上,但晶粒聚集长大到5 μm左右.研究发现Mo-Cu复合粉末形成了亚稳态的超饱和Mo(Cu)固溶体,随着烧结温度的升高,Cu相逐渐从亚稳态的超饱和Mo(Cu)固溶体颗粒中析出.     

放电等离子烧结制备纳米晶双相耦合(NdDy)11.5(FeCoNb)82.4B6.1致密磁体

使用放电等离子烧结(SPS)制备致密的纳米晶交换耦合Nd_2Fe_(14)B/α-Fe永磁合金.研究烧结温度、时间、压力对合金磁性能和显微组织的影响.结果表明,随温度、压力的升高,密度增大,磁能积增加;但温度过高或时间过长,使得晶粒长大,导致矫顽力降低.在烧结压力为500 MPa,烧结温度为700 ℃保温3 min后,得到密度为7.6 g/cm~3,晶粒细小的致密块体,其磁性能为:B_r=0.81 T,H_(ci) =856 kA·m~(-1),(BH)_m =106 kJ·m~(-3),其晶粒大小约20 nm.     

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。