混合稀土阻燃ZM5合金表面氧化膜再生能力研究

将ZM5-0.1%RE合金加热到800℃,当表面氧化膜形成后,冷却至室温,去除表面氧化膜,制成经过氧化的ZM5-0.1%RE合金,通过分析该合金的TGA曲线、恒温氧化动力学曲线以及表面氧化膜的XRD谱,对其表面氧化行为进行研究。结果表明:该合金具有良好的杭氧化性,氧化质量增加主要发生在400～700℃;该合金在600、700℃的氧化动力学曲线遵循抛物线规律,在合金表面生成了一层由(RE)2O3、MgO、Al2O3、Mg17Al12组成的厚度为4.0～5.5μm致密氧化膜,以抑制基体镁合金的进一步氧化;说明ZM5-0.1%RE合金表面氧化膜具有良好的再生能力。     

含Li_2CO_3的电解液中形成ZAlSi12Cu2Mg1合金微弧氧化膜的表征

在Na2SiO3+NaOH体系电解液中加入Li2CO3调整电解液组成,对ZAlSi12Cu2Mg1合金进行微弧氧化。利用涡流测厚仪、XRD、SEM、EDS对氧化膜进行表征。结果表明:Li2CO3含量从4.0g/L增加到6.0g/L,膜层厚度从71μm增加到126μm;微弧氧化过程中,随氧化时间的延长电流呈下降趋势,且随着Li2CO3含量的增多,电流下降速率增大;SEM分析可知,随Li2CO3加入量的增加试样表面氧化膜的粗糙程度先降低后增加,膜层表面微孔数量减少,孔径增大,呈现出的熔融状态更为明显;XRD分析表明,氧化膜主要由Mullite和Al2O3相组成。由EDS分析可知,氧化膜表面主要分布有O、Al和Si及少量的Na和Mg元素。     

Cu-Mg合金抗氧化性能的研究

利用SEM、EPMA、SIMS和热重分析等不同测试手段,研究了3种不同Mg含量的铜合金经退火后在400～900℃的抗氧化性能.结果表明:在H2气氛下退火后,Cu-Mg合金表面生成了MgO氧化膜,合金中Mg的含量对氧化膜的形貌及随后的高温抗氧化能力有很大影响.3种Cu-Mg合金在高温下的氧化速率均遵循抛物线规律,且氧化速率随温度的升高而增加.当合金在400～700℃氧化时,w(Mg)=0.34%的合金由于退火后表面生成的氧化膜平滑、致密,阻碍了高温氧化时氧元素向合金内部的扩散,氧化速率最小.     

纳米化对M951合金高温氧化性能的影响

采用磁控溅射的方法在M951铸造合金表面制备了相同成分的纳米晶涂层,研究了涂层在1 000℃和1 100℃空气中的恒温氧化行为及在1 000℃空气中的循环氧化行为,并与粗晶合金进行了对比。同时利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱分析仪(EDX)和透射电子显微镜(TEM)对合金及涂层样品氧化前后的微观形貌及相组成进行了分析。结果表明:1 000℃恒温氧化后合金表面形成了连续的以Al2O3为主的氧化膜;1 000℃循环氧化及1 100℃恒温氧化后合金表面氧化物分层,外层为NiAl2O4,内层为Al2O3,合金中形成了富Nb的内氧化物,氧化膜发生明显开裂和剥落。而在上述所有试验条件下,纳米晶涂层表面都形成了薄而连续且粘附性好的α-Al2O3保护性氧化膜。纳米化促进了M951合金表面以Al2O3为主的氧化膜的形成,增强了氧化膜的粘附性,显著提高了合金的抗氧化性能。     

铝真空钎焊的冶金研究

用光学显微镜和电子显微镜研究了Al-Si-Mg合金在加热到钎焊温度过程中所发生的组织变化。为了探讨合金在加热期间表面氧化物成分的变化。还进行了俄歇表面分析。结果表明,钎料合金中的Mg和别的元素与Al和Si形成了低熔点共晶物。当达到共晶温度时,发生了局部熔化,同时氧化膜破裂,并向表面渗流。在真空条件下,熔化的共晶由于蒸发和重新凝固而失掉了Mg,这个过程随着时间的增加和温度的提高,循环反复,直至整个表面完全由纯净的金属组成为止。这样的表面一直保持到接近于Al-Si共晶的温度(577℃),这时金属发生明显峰流,钎焊开始进行。俄歇表面分析表明,针料合金表面氧化物在400℃以上几乎完全都是MgO。在共晶温度下由于渗流形成新的表面以后,其氧化膜的厚度达到最小值。在高温下氧化膜厚度的增加可由炉子条件和材料性能决定。良好的钎焊性能与Mg在钎料合金中的物理作用和化学作用都有关系。     

晶粒细化对Cu—20Ni—20Cr合金氧化行为的影响

为探讨晶粒尺寸变化对三元复相合金氧化行为的影响，采用机械合金化制备了纳米晶三元Cu-20Ni-20Cr合金，并对比研究了该合金与同成分的铸态合金在700℃～800℃，0．1MPa纯氧气中的氧化行为。结果表明，铸态合金表面没有形成连续的Cr2O，保护膜，而是形成了含有所有组元氧化物及它们复合氧化物的复杂氧化膜结构。纳米晶Cu—20Ni—20Cr合金在700℃时合金表面形成了连续的Cr2O3氧化膜，而800℃时虽没有形成Cr2O3外氧化膜，但氧化膜规则平坦，外层是CuO，中间层是Cu2O，NiO和Cr2O3组成的混合氧化物区，内层则形成了一薄但不连续的Cr2O3层。晶粒细化降低了合金表面形成Cr2O3氧化膜所需活泼组元Cr的临界浓度。     

高温预氧化膜锆合金的腐蚀性能

南韩高等工程研究院和汉阳大学材料科学与工程系对用于核燃料包套的锆-4合金表面进行了预氧化处理，并研究了处理后的合金在360℃下的腐蚀性能。他们将常规的锆-4合金用20ψ%氧气加80ψ%氩气的混合气体分别在700℃和1100℃下退火以形成预氧化膜，随后将形成预氧化膜的合金在装有纯净水的高压釜中进行氧化试验，试验温度为360℃，压力为1800MPa。合金在混合气体中预氧化时形成的预氧化膜厚度与氧化时间的关系可用下式描述：     

MA956和Fecraloy两种合金氧化膜的断裂应变

利用四点弯曲／声发射方法在室温下测量了ＨＡ９５６和Ｆｅｃｒａｌｏｙ合金表面形成的氧化膜的断裂应变。结果表明，在张应力作用下，ＭＡ９５６合金在１０００℃、１１００℃和℃三种温度以下及Ｆｅｃｒａｌｏｙ合金在１２００℃下不同时间氧化后形成的膜的断裂应变几乎不变，分别约为０．３４％和０．１３％。这两种合金氧化时都主要形成Ａｌ２Ｏ３。ＭＡ９５６合金氧化膜在实验时间范围内从未发现有开裂，而Ｆｅｃｒａｌｏｙ合金     

Al-25Cu-12Mg合金的高温氧化行为研究

采用X射线衍射技术、扫描电子分析等分析方法,对Al-25Cu-12Mg合金的高温氧化行为、氧化层的形貌和成分进行了分析。结果表明,Al-25Cu-12Mg合金在同一温度下进行高温氧化,随氧化时间增加,氧化增重不断增加;在氧化时间相同时,随氧化温度升高,氧化增重显著增加。Al-25Cu-12Mg合金在温度较低时,样品基本上不氧化,只在样品表面形成一层氧化膜,阻止样品继续氧化;在温度较高时,随氧化时间的延长,样品表面形成的氧化膜遭到破坏,氧化膜破裂剥落,已不能阻止样品的继续氧化。     

V对Zr-1Nb-0.1Fe合金显微组织及耐腐蚀性能的影响

采用真空自耗电弧炉熔炼制备了Zr-1Nb-0.1Fe和Zr-1Nb-0.1Fe-0.05V合金,通过OM、SEM和XRD观察分析了两种合金的金相组织、第二相粒子以及在360℃、18.6MPa条件下在LiOH与硼酸配制的Li+B水溶液中长期腐蚀后的腐蚀氧化膜相组成,研究了V对Zr-1Nb-0.1Fe合金微观组织及耐腐蚀性能的影响。结果表明,Zr-1Nb-0.1Fe合金中添加0.05%的V能够细化组织晶粒,形成尺寸较小且弥散分布的第二相粒子,并改变Zr-1Nb-0.1Fe合金在Li+B水溶液中氧化膜微晶结构,具有稳定氧化膜的四方相(tZrO_2),提高了合金在360℃、18.6MPa条件下的Li+B水溶液中的耐腐蚀性能。     

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。