(Zr0.67Ni0.33)100-xPdx(X=0、5、10、20)非晶合金的晶化行为

通过单辊快淬制备(Zr0.67Ni0.33)100-xPdx(x=0、5、10、20)非晶态合金,利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)和高分辨电镜(HREM)研究了上述合金的晶化过程。结果表明,加入Pd后合金由1个晶化反应转变为2个晶化反应。当Pd的加入量为5at%时,初生相仍为Zr2Ni,随后部分残留非晶转变为Zr2Pd;当Pd的加入量达到10at%时,初生相为Zr2Ni和少量Zr2Pd并存;当Pd的加入量达到20at%时,初生相为明显的Zr2Pd。     

加载方式对Zr基非晶复合材料变形行为的影响

制备了含有8at%Ta元素的Zr基相应的非晶复合材料和Zr基完全非晶合金,研究了其在压缩和弯曲两种加载方式下的变形行为。结果发现,在压缩过程中,Ta固溶体粒子的存在可以阻碍剪切带的扩展,促使多重剪切带的萌生。因此,Ta固溶体相的存在可以有效的改善非晶合金的压缩塑性而不降低其强度;弯曲加载过程中,由于Ta固溶体和非晶基体的模量以及强度差异,两者的界面处会产生大的应力集中,在连续载荷的作用下,裂纹迅速沿着两者的界面形成并开裂,最终导致该非晶复合材料的失效,同时,相比于完全非晶合金,其断口上的临界剪切位移显著减少,且与Ta固溶体相的尺寸相当,因而Ta固溶体相的存在降低了非晶合金的弯曲塑性变形能力。     

Cu44.25Ag14.75Zr36Ti5非晶合金的晶化行为

采用铜模铸造法制备了直径为3mm的柱状Cu44.25Ag14.75Zr36Ti5块体非晶合金,X射线衍射证明试样为完全非晶态。利用差示扫描热分析仪(DSC)、X射线衍射,研究了该非晶合金的晶化行为。利用Kissinger和Ozawa方程求得Cu44.25Ag14.75Zr36Ti5第一晶化峰和第二晶化峰的晶化激活能。结果表明,该大块非晶合金具有良好的热稳定性,在10K/min的加热速率下,析出相主要是Cu8Zr3和Cu10Zr7。     

非晶态Zr47Ni30Ti23合金中纳米晶的发展

非晶材料的纳米晶化可在非晶基体中弥散分布纳米晶粒制成纳米晶/非晶复合材料，从而提高力学/物理性能。为此韩国人介绍了非晶Zr47Ni30Ti23合金的纳米晶形成过程。 首先用高纯Ti，Zr，Ni原料用氩弧熔炼成合金锭。用熔融旋转法以30m/s的筒表面速度摔成非晶带，用差式扫描量热计(DSC)以 20℃/min~40℃/min的加热/冷却速度，在氩气下研究非晶带的晶化行为，用X射线衍射(XRD)和透射电镜(TEM)分析和标定结晶相 的结构和形态。由Zr-Ni-Ti三元相图可知，Zr47Ni30Ti23合金中的平衡相包含大量的Laves相和Zr2Ni相及少量α-Zr(Ti)固溶体。…     

Zr-Ti-Cu-Ni-Be大块非晶合金等温晶化过程相分离研究

利用差示扫描量热法(DSC)和透射电镜(TEM)对Zr41.2Ti13.8Cu12.5Ni10Be22.5(at％)大块非晶合金的等温晶化过程和析出相进行了研究。结果表明，大块非晶合金在等温晶化过程中表现出多阶段相析出行为，并且在不同的晶化阶段，析出相也有所不同。在第1个晶化阶段，析出相主要是体心四方(b.c．t)结构的Zr2Cu相；而在晶化的第2个阶段，晶化相主要为简单六方结构的ZrBe2相。从一定程度上证实了Zr41.2Ti13.8Cu12.5Ni10Be22.5大块非晶合金在发生晶化时会形成富Zr区和富Be区，即有相分离的趋势。XRD测试的结果也证实了非晶合金在发生完全晶化时，主要的晶化产物为Zr2Cu和ZrBe2相。     

块体非晶合金Cu58 Zr30 Ti10 Sn2的形成与晶化行为研究

采用铜模吸铸法制备了直径为2～3mm的圆柱状Cu60-xZr30Ti10Snx（x=0、1、2）块体非晶合金。用X射线衍射（XRD）和差式扫描量热仪（DSC）研究了非晶合金的结构、热稳定性和晶化特征，非晶合金Cu60-xZr30Ti10Snx的特征温度Tg、Tx、△Tx=（Tx-Tg）均与Sn含量相关。块体非晶合金Cu58Zr30Ti10Sn2的Tg为703．9K、Tx为755．5K、△Tx约为51．6K。这些特征温度随DSC升温速率的增大，不断向高温区偏移，其中晶化行为的这种动力学效应比其玻璃转变的更为显著。由Kissinger法获得的块体非晶合金Cu58Zr30Ti10Sn2的玻璃转变激活能Eg为3．30eV、晶化激活能Ex为3．17eV、第一晶化峰激活能Ep1为2．82eV、第二晶化峰激活能Ep2为3．13eV。由Ozawa法获得的各激活能比Kissinger法的相应数值稍偏低，但趋势是一致的。     

Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金晶化行为研究

用示差扫描量热仪（DSC）研究了Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金的匀速升温晶化与等温晶化的晶化行为。在匀速升温晶化方式下，用Kissinger法与Ozawa法获得了块体非晶合金的激活能，对第一晶化峰分别为320．5kJ／mol和316．6kJ／mol，对第二晶化峰分别为324．5kJ／mol和320．5kJ／mol。该非晶合金的晶化表现出明显的动力学效应。在等温晶化方式下，用Johnson-Mehl-Avrami方程获得了晶化的Avrami指数为1．61，表明非晶合金的晶化受原子扩散控制。     

镁基块体金属玻璃基复合材料研究

在空气中采用普通铜模浇铸法制备了两种成分的Mg-Cu-Al-Y金属玻璃复合材料（Mg65Cu23Al2Y10和Mg65Cu20Al5Y10）试样。XRD分析表明，随着Al的加入，原本的非晶“馒头峰”上出现了晶体增强相的尖锐峰；DSC曲线中晶化放热峰表明两种合金基体为非品态结构．相比于纯玻璃态时，复合材料的玻璃转变温度和初始晶化温度均下降，过冷液相区变窄，同时表现为多级晶化；尽管两种合金的成分只有细微差别，但微观组织却相差很大．当Al含量为2％时，显微组织中有明显的针状组织存在．而Al含量为5％时，为粒状组织.显微硬度测试表明：当Al含量为2％时．硬度值明显提高，均值达到了276HV，比完全非晶态下的硬度值高出42HV。     

一种新的具有室温大塑性的Zr基块体非晶合金

通过二元共晶比例法设计了一种新的具有室温大塑性的Zr51Al9.96Ni14.34Cu24.7块体非晶合金.该合金室温压缩最大强度达2356 MPa,塑性应变达14.6%.高分辨透射电镜(HRTEM)及热分析(DSC)结果表明,压缩过程的变形诱发了纳米晶化.纳米晶的形成一方面诱发新的剪切带的形成,增加了剪切带的密度;另一方面阻碍了剪切带的进一步扩展,使大量初始剪切带与二次剪切带的交割和分叉,因而导致所研究非晶合金优异的塑性变形能力.     

Zr65Cu12.5Ni10Al7.5Ag5玻璃合金初期晶化结构的电子显微分析

采用等温差示扫描量热分析(DSC)和透射电镜(TEM)观察相结合的方法,研究了Zr65CU12.5Ni10AI7.5Ag5非晶合金玻璃转变和晶化过程.利用DSC对合金晶化过程实时监控,在加热到不同温度随炉冷却退火后对样品进行TEM分析,观察其不同阶段的微观结构变化,揭示其晶化特征.结果发现:Zr65Cu12.5Ni10Al7.5Ag5急冷合金晶化过程分为3段.初期晶化相为二十面体准晶I相,在I相与非晶基体之间没有明显的成分差异,准晶相相比于非晶基底略富Zr贫Cu;初期二十面体准晶相形核密度高生长迅速,通过消耗非晶相紧密堆积生长:晶化第1阶段结束后仍有残余非晶相存在.     

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。