液-液掺杂钼镧合金中的稀土相研究

采用液-液掺杂方式及溶胶-凝胶技术制备出稀土镧掺杂钼粉,经等静压、烧结制成掺镧钼坯。利用XRD、SEM、EDS、TEM等检测手段对不同加工态下材料的组织、形貌及稀土相进行了分析。结果表明：硝酸镧La(NO3)3溶液与仲钼酸铵(NH4)6Mo7O24·4H2O溶液发生化学反应生成钼酸镧La2(MoO4)3,经焙解和还原,稀土相以La2O3的形式存在于Mo粉中,并起到细化钼颗粒的作用;烧结成坯后,La2O3弥散分布在钼基体中     

玻璃先驱体对溶胶-凝胶合成纳米氧化铝的影响

以硝酸铝、硝酸镁、硝酸钙、硅溶胶为原料,采用溶胶-凝胶法合成纳米级氧化铝粉体,并对不同温度煅烧后粉体的物相与形貌进行表征。通过在硝酸铝的溶胶中引入4%(质量分数)的MgO-CaO-Al2O3-SiO2玻璃助剂先驱体,在80℃水浴中长时间静置后获得乳白色凝胶,在不同温度下煅烧该凝胶,结果发现:煅烧温度低于950℃时,所获得的粉体主要为无定型态,仅含有少量的γ型氧化铝;将凝胶在1000℃煅烧2h后,全部变成粒度在25～35nm、粉体颗粒呈球形的α型氧化铝;玻璃助剂先驱体的添加,不但降低了α-Al2O3的合成温度,同时还加快了γ-Al2O3向α-Al2O3的转变进程。     

溶胶-凝胶/高温氢还原工艺制备Mo-Al2O3-La2O3复合粉末

Al₂O₃协同La₂O₃强韧化的钼及钼合金具有优越的综合力学性能，通过粉末冶金方法制备钼及钼合金的关键在于获得超细或纳米Mo-Al₂O₃-La₂O₃粉末。本文以仲钼酸铵、硝酸铝、硝酸镧和柠檬酸为原料，采用溶胶-凝胶-煅烧-高温氢还原工艺制备Mo-Al₂O₃-La₂O₃复合粉末，利用XRD、SEM、EDS和TEM等分析手段对粉末的微观组织结构进行表征。结果表明：当水浴温度为85℃、p H=1、柠檬酸与钼酸铵的质量比为1.7时，形成了网状结构大分子交联的络合物前驱体，这有利于在后续高温还原过程中制备超细或纳米Mo复合粉末。前驱体粉体在550℃煅烧3 h后，粉末主要由MoO₃和Al₂(Mo O₄)₃组成。采用一步高温氢还原时，还原3 h后MoO<...     

MoO3纳米纤维的制备及其氢还原特性研究

以仲钼酸铵和硝酸为原料通过水热法在170 ℃下恒温40 h获得直径为50～100 nm、长度大于20 μm的MoO3纳米纤维.在450～650 ℃的不同温度下对所合成的MoO3纳米纤维进行氢气还原,利用XRD和FSEM对还原样品进行表征.结果发现,MoO3纳米纤维在450 ℃的还原温度下有MoO2形成,在600 ℃的温度下被完全还原成粒度为0.1～2 μm的Mo粉.在还原过程中,大部分MoO3纳米纤维形状不具有继承性,而处于自由空间的小部分单根MoO3纳米纤维可以转化成针状Mo颗粒.     

热处理工艺对纳米γ-Al2O3粉体的尺寸和形貌的影响

以异丙醇铝为原料采用溶胶凝胶技术制备水合氧化铝前驱体,经热处理制得纳米氧化铝粉体.采用正交实验设计研究了热处理工艺条件对纳米氧化铝粉体的尺寸和形貌的影响规律.结果表明,热处理工艺参数对Al2O3粒子颗粒特性的影响由强到弱的次序为:煅烧温度、水合氧化铝在300℃分解温度点的保温时间、在煅烧温度点的保温时间;通过控制其热处理工艺参数,可获得一定尺寸范围的大小均匀,分散性好的球形γ-Al2O3粉体;制备尺寸为8 nm的球形γ-Al2O3粉体的最佳的热处理工艺参数为:煅烧温度900℃,在煅烧温度点保温4 h,在300℃温度点不保温.     

煤系硫铁矿浮选尾矿热化学活化脱硅制备铝精矿

提出热活化脱硅技术处理某煤系硫铁矿浮选尾矿制备铝精矿,对制备氧化铝精矿的工艺制度及脱硅机理进行研究。结果表明:该尾矿适宜的热化学活化脱硅制度为活化焙烧温度1 150℃、焙烧时间15～20 min、碱浸溶硅温度125～140℃、溶出时间30 min、NaOH浓度140 g/L。在此条件下,对Al2O3和SiO2含量分别为46.22%和28.33%(质量分数)的硫铁矿浮选尾矿,焙砂SiO2溶出率达到71.91%,所得铝精矿中Al2O3含量达69.29%,铝硅比5.59。XRD结果表明:硫铁矿尾矿中伊利蒙脱石、高岭石和叶腊石等铝硅酸矿物在焙烧过程中活化分解生成无定形SiO2和少量莫来石,与此同时,一水硬铝石转变成α-Al2O3。在焙砂的碱浸过程中,无定形SiO2溶解于NaOH溶液被脱除,而α-Al2O3和莫来石不能溶解,同时生成的水合铝硅酸钠(Na8Al6Si6O24(OH)2(H2O)2)将导致SiO2溶出率降低。焙烧过程中尾矿中的黄铁矿转化为赤铁矿、锐钛矿部分转化成金红石,在碱浸过程中它们均不会溶解而进入铝精矿中。     

工业污泥制备氧化铝的实验研究

以工业污泥为原料，分别利用双水解和通人二氧化碳气体的方法制备Al（OH）3（胶体），在1100℃煅烧后制得α-Al2O3粉体。并通过场发射扫描电镜（FESEM）、能量发射能谱（EDS）以及X衍射仪（XRD）研究污泥原料、Al（OH），（胶体）和α-Al2O3粉体的形貌、成分和结构。结果表明：两种方法中，双水解的方法制备α—Al2O3工艺简单？产物杂质少、产量高。EDS分析结果显示：氧化铝平均纯度达98％。     

Al2O3/Al2(1-0.2)Mg0.2Ti(1+0.2)O5基复相陶瓷的制备及其性能

以工业级α-Al2O3、金红石型TiO2和轻质MgO粉体为原料,过量配置α-Al2O3,采用固相反应法于1400℃煅烧实现了Al2O2/Al2(1-0.2)Mgg0.2Ti(1+0.2)O5基复相粉体的原位合成,实现两相的均匀混合,原位制备出性能良好的Al2O3/Al2(1-0.2)Mg0.2Ti(1+0.2)O5基复相陶瓷.利用XRD对原位合成的复相陶瓷粉体的相组成进行了表征,利用FESEM观察了复相陶瓷的断口形貌,测量了复相陶瓷的烧结密度、抗弯强度和热膨胀系数,研究了第二相Al2O3的引入量对钛酸铝基陶瓷的微观结构、抗弯强度和热膨胀性能的影响.结果显示,当复相Al2O3的引入量为15%(质量分数)时,钛酸铝基复相陶瓷的抗弯强度提高到108 MPa,并且具有较低地热膨胀系数0.7×10-6 /℃.     

氟盐对炼镁还原渣中氧化铝浸出率的影响研究

以白云石和菱镁石为原料以铝粉为还原剂真空热还原炼镁过程中添加氟化钙可使镁还原率提高5%以上,还原温度降低50℃,还原后还原渣的主要物相为CaO.2Al2O3,加入的氟化钙在还原过程会参与反应生成氟铝酸钙。在实验室以氢氧化钠和碳酸钠的混合碱液对该含氟盐还原渣中氧化铝的浸出进行了研究,研究结果表明:经碱液浸出后还原渣中的CaO.2Al2O3全部被分解,还原渣中的氧化铝浸出率在70%以上,浸出渣的主要物相为CaCO3。含氟盐炼镁还原中氧化铝的浸出率比不含氟盐的氧化铝浸出率低10%以上,在还原过程中生成的氟铝酸钙和浸出过程中生成的水合铝酸钙是导致氧化铝损失增加的主要原因。     

硫酸氢铵焙烧粉煤灰提取氧化铝(英文)

采用NH4HSO4焙烧法从粉煤灰中提取Al2O3。首先,通过NH4HSO4焙烧和去离子水浸出法提取粉煤灰中的Al和Fe;然后,加入NH4HCO3溶液沉淀浸出液中的Al和Fe,利用NaOH溶液浸出得到的Al(OH)3和Fe(OH)3混合沉淀,所得铝酸钠溶液经碳酸化分解得到纯净的Al(OH)3;最后,煅烧纯净的Al(OH)3制备α-Al2O3产品。通过实验确定各工艺流程的最佳条件。制备的α-Al2O3产品达到YS/T 274-1998标准的工艺指标。     

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).     

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.     

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.     

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。