CeO2颗粒对铌合金表面镀渗复合涂层抗氧化性能的影响

为了提高铌合金的高温抗氧化性,采用化学镀结合包埋渗技术在铌合金表面制备了含有CeO_2颗粒的复合涂层,研究了复合涂层的微观结构和高温抗氧化性能。结果表明,不含CeO_2的Al/Ni涂层以NiAl相为主,Al/Ni-CeO_2涂层则含NiAl、NiAl_3、Al3Nb和CeO_2等相。经1000℃氧化测试,Al/Ni复合涂层氧化50 h后增重为8.0 mg/cm~2,表面主要生成Al_2O_3、AlNbO_4相;Al/Ni-CeO_2复合涂层50 h后氧化增重为4.0 mg/cm~2,表面以Al_2O_3、CeO_2、NiAl、NiAl_3、Al3Nb、AlNbO_4相为主。高温氧化后,2种涂层样品表面均生成连续致密的Al_2O_3膜,涂层与基体结合良好;含CeO_2的涂层,其稀土氧化物主要在Ni膜拖拽力作用下富集于涂层互扩散区。稀土氧化物颗粒的添加细化涂层组织,降低涂层中Al元素的消耗,填补涂层中的孔洞,增强了氧化膜与涂层的粘附力,有效提高了涂层的抗氧化性。     

一种新型细晶Ni3Al涂层抗高温氧化性能研究

通过600℃/2 h真空退火,使复合电沉积的Ni-14.1 mass%Al膜(平均粒径为1 μm)合金化,获得一种新型细晶Ni3Al涂层.对比研究了该涂层与粗晶Ni3Al合金900℃下50 h恒温氧化过程.结果表明,细晶涂层可快速生长连续Al2O3膜,导致NiO的生长受到明显抑制.与粗晶合金相比,该氧化膜粘附性更强.其...     

DD98M纳米晶AlSi渗层制备及抗高温腐蚀性能研究

采用磁控溅射技术在DD98M合金表面制备了同成份的纳米晶,采用多弧离子镀技术在DD98M纳米晶涂层表面沉积了AlSi涂层,对上述制备态纳米晶+AlSi复合涂层进行了真空扩散处理,得到了外层为β-NiAl层、内层为γ'-Ni_3Al层的双层结构复合涂层。研究了合金、DD98M纳米晶涂层及复合涂层在1050℃恒温氧化及900℃下Na_2SO_4+25%K_2SO_4混合熔盐体系中的热腐蚀行为。结果表明:1050℃恒温氧化时,DD98M合金表面生成NiO,α-Al_2O_3,Ta_(0.8)O_2,CrTaO_4及NiAl_2O_4等组成的混合氧化物膜,氧化膜开裂剥落严重。纳米晶涂层表面生成α-Al_2O_3和少量NiAl_2O_4组成的混合氧化物膜,复合涂层表面形成了均匀致密的单一α-Al_2O_3膜。纳米晶涂层和复合涂层大幅提高了合金的抗恒温氧化性能。在900℃下Na_2SO_4+25%K_2SO_4熔盐中,DD98M合金20 h后即发生了灾难性腐蚀,沉积态纳米晶及其预氧化涂层提高了合金的抗热腐蚀性能,复合涂层大幅提高了合金的抗热腐蚀性能。     

CORRELATION BETWEEN OXIDATION BEHAVIOUR AND BORON CONTENT IN Ni_3Al

本文研究了含硼量为0-2.22at.-％的Ni_3Al在750-1150℃和3-100h条件下的氧化行为。结果表明,不同硼含量的Ni_3Al合金在不同温度下的氧化动力学曲线基本都符合抛物线规律。硼含量在0.52-1.37at。-％时抗氧化性能最好。研究了氧化膜的形态与结构。0-1.37at.-％B的Ni_3Al合金,表面形成以Al_2O_3为主的氧化膜,并含有少量NiO和NiAl_2O_4,含有2.22at.-％B的Ni_3Al合金,表面生成复杂的硼氧化物,破坏Al_2O_3膜的完整性,抗氧化性最差。但无硼合金中,NiAl_2O_4的含量最高,并在试样冷却过程中几乎全部剥离。     

Ti6Al4V合金表面激光熔覆NiCrAlSi复合涂层的组织及高温抗氧化性能

为提高Ti6Al4V合金的高温抗氧化性能,以Ni80Cr20-40Al-20Si(质量分数,%)复合合金粉末为原料,采用激光熔覆技术,在Ti6Al4V合金表面制备复合涂层,系统地分析涂层的物相、显微组织结构及高温抗氧化性能。结果表明:复合涂层中没有发现裂纹,仅有少量气孔,且与基体实现良好的冶金结合;Ti_5Si_3/Al_3Ni_2作为增强相均匀分布于基体Al_3Ti/NiTi中;经恒温800℃氧化32 h后,复合涂层的氧化膜主要由Al_2O_3和NiO组成,结构连续致密,氧化动力学曲线近似符合抛物线规律,表现出较好的高温抗氧化性能;而Ti6Al4V合金的氧化膜主要为疏松的TiO_2,表面氧化严重,表现出较差的抗氧化性能。激光熔覆NiCrAlSi复合涂层可望成为有效提高Ti6Al4V合金高温抗氧化性能的途径之一。     

含铝奥氏体耐热钢的高温抗氧化性能

以Fe-18Cr-30Ni为基础,添加不同含量的Al设计了4组新型奥氏体耐热钢。利用氧化质量增加法研究了4组新型奥氏体耐热钢在700、800和900℃下空气中的氧化行为,绘制了氧化动力学质量增加曲线,并利用XRD、SEM和EDS对氧化膜的表面形貌及结构进行了表征。结果表明,1~3号钢在900℃时均形成了较为致密的Al2O3内层氧化膜,合金表面生成的复合氧化膜由内到外依次为Al_2O_3、(Al_(0.9)Cr_(0.1))_2O_3、尖晶石氧化物Fe(Cr,Al)_2O_4;1号钢氧化过程中还形成了富(Cr,Fe)的混合氧化物,降低了Al_2O_3氧化膜的连续性;4号钢900℃并没有形成致密的Al_2O_3内层氧化膜,生成的复合氧化膜由内到外依次为(Al_(0.9)Cr_(0.1))_2O_3、尖晶石氧化物Fe(Cr,Al)_2O_4。     

以铝和碳酸镍为原料机械合金化及后续退火制备铝酸镍纳米陶瓷（英文）

通过高能球磨Ni CO_3和Al粉后退火制备纯NiAl_2O_4。采用X射线衍射、差热扫描、热重分析、扫描电子显微镜和透射电子显微镜研究粉末样品的相组成、热学行为、形貌和组织。从Ni CO_3和Al粉中合成尖晶石结构NiAl_2O_4分为三步:Al氧化成Al_2O_3,碳酸镍分解为Ni O和CO2,最后Al2O3与Ni O发生固相反应。Ni CO_3/Al混合物经5 h机械球磨后于900°C退火2 h即可形成NiAl_2O_4单相,退火温度比传统固相方法低约500°C。透射电子显微镜结果表明,所得尖晶石结构的NiAl_2O_4化合物的粒径小于100 nm。     

TiAlSiN涂层对γ-TiAl基合金抗高温氧化性能的影响

采用多弧离子镀的方法在两种γ-TiAl基合金(Ti-46Al-2.5V-1Cr-0.3Ni和Ti-48Al-2Cr-2Nb,原子分数)表面制备了TiAlSiN涂层,研究了样品在800℃下空气中的循环氧化行为。在800℃循环氧化300 h后,γ-TiAl基合金表面都形成了TiO_2和Al_2O_3混合氧化物膜,氧化膜分层;Ti-46Al-2.5V-1Cr-0.3Ni合金表面氧化膜较厚且剥落严重,而Ti-48Al-2Cr-2Nb合金氧化膜较薄,只发生了轻微剥落。表面施加Al、Si含量不同的TiAlSiN涂层显著降低了TiAl基合金的氧化速率,涂层表面氧化膜主要由TiO_2和α-Al_2O_3组成。Ti_(0.5)Al_(0.4)Si_(0.1)N和Ti_(0.5)Al_(0.45)Si_(0.05)N两种涂层样品表面氧化膜薄而致密,涂层未发生明显退化;Ti_(0.6)Al_(0.3)Si_(0.1)N涂层样品表面氧化膜相对较厚。Al含量较高的Ti_(0.5)Al_(0.4)Si_(0.1)N和Ti_(0.5)Al_(0.45)Si_(0.05)N涂层抗氧化性能优于Al含量较低的Ti_(0.6)Al_(0.3)Si_(0.1)N涂层的。TiAlSiN涂层与TiAl基合金之间只发生了轻微互扩散。     

新型镍基高温合金1100℃氧化行为的研究

利用X射线衍射(XRD)、扫描电镜与能谱(SEM/EDS)、激光拉曼光谱(Raman)研究了新型镍基高温合金1 100℃氧化行为。结果表明,氧化增重基本遵循抛物线规律,约氧化100 h后氧化增重趋于稳定。在氧化初期,内层形成均匀连续的Al_2O_3氧化膜,中间层主要由NiAl_2O_4组成,外层氧化膜由NiFe_2O_4、Fe_2O_3、NiCr_2O_4和Cr_2O_3组成。随着氧化时间的延长,外层及中间层氧化膜逐渐变得疏松并脱落,而内层逐渐形成连续致密的Al_2O_3氧化膜。根据氧化膜的组成进一步分析了合金的氧化机制。该新型镍基高温合金具有优异的抗高温氧化性,可在1 100℃长期使用。     

钛及钛合金高温氧化行为研究

对工业纯钛TA2、TC4及Ti60合金分别在600、700、800℃进行氧化,得到氧化增重曲线。利用SEM、XRD等手段对氧化表面形貌、氧化产物构成及分布进行研究并分析了3种钛材在不同温度下的氧化机制。结果表明:随着温度升高,TA2、TC4以及Ti60三种钛材的抗氧化能力均有所下降,且抗氧化能力由强到弱依次为Ti60TA2TC4。工业纯钛TA2的氧化产物为TiO_2,TC4合金在600℃氧化产物为TiO_2,700、800℃为TiO_2/Al_2O_3,Ti60合金氧化产物为TiO_2/Al_2O_3。TA2和TC4钛合金在600℃时的氧化反应均受扩散过程控制,随温度升高(700、800℃),逐渐转变为界面反应控制。由于氧化产物组织结构疏松且Al_2O_3、TiO_2和基体由于热膨胀系数不同导致的应力,TC4合金氧化膜易剥落,抗氧化能力较差。Ti60合金在700、800℃的氧化反应也受扩散过程控制,Zr、Si及稀土元素的添加得到保护能力较强的致密氧化膜Al_2O_3,抗氧化能力较好。然而800℃时,富Sn、Nd相的析出诱导氧化膜剥离,抗氧化能力有所下降。     

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。