机械合金化扩展Fe—Cu系固溶范围

机械合金化法可使室温下不互溶体系Fe_(1-x)Cu_x形成过饱和固溶体。X射线衍射实验表明;当x≤0.15时为具有Fe的bcc结构固溶体;当x≥0.40时具有Cu的fcc结构固溶体;当0.15相似文献   

热处理和熔炼方式改变对AlCoCrFeNiTi0.2高熵合金的影响

采用电弧熔炼方法设计制备了AlCo CrFeNiTi_(0.2)合金,发现铸态时的合金形成了B2相和bcc相,且室温压缩性能良好,压缩塑性为32.6%,屈服强度为1530.4 MPa,抗压强度为4035.0 MPa,硬度接近6000 MPa。在550、800和1050℃对其进行热处理,采用水冷的方式以保存高温相,3个温度对应的相组成分别为bcc+B2、bcc+B2+fcc+σ和bcc+B2+fcc,热处理后合金脆性和硬度升高。采用磁悬浮熔炼制备了大块AlCo CrFeNiTi_(0.2)合金,该状态合金成分分布比较均匀,形成了bcc+B2+σ3相,在600℃时压缩塑性为35.0%,且仍能保持1486.7 MPa的屈服强度,耐高温性能较好。     

基于第一性原理计算V元素对高熵合金Al0.4Co0.5VxFeNi的组织及性能影响

采用第一性密度泛函理论,结合虚拟晶体近似（VCA）的方法建立晶体结构模型,开展高熵合金Al0.4Co0.5Vx FeNi的结构性能、弹性性能及基态能量计算。根据能量最低原理可确定,Al0.4Co0.5Vx FeNi高熵合金的最优K-point值为12×12×12,截断能为1000 eV。计算结果表明：Al0.4Co0.5Vx FeNi系高熵合金均可生成fcc+bcc结构,fcc的力学稳定性明显优于bcc的力学稳定性。V元素含量由0.2增至0.8时,bcc点阵常数降低约4%,fcc晶格常数降低约6%。随着V元素的增加,Al0.4Co0.5Vx FeNi合金的体模量、剪切模量逐渐减小。V元素含量为0.8时,bcc结构的泊松比异常增加,进一步说明了随着V元素含量的增加,材料的塑性变形能力降低,材料的脆性增加。经试验验证,Al0.4Co0.5Vx FeNi系高熵合金均由fcc和bcc组成,组织形貌均为两相组织;V元素含量由0.2升至0.8时,延伸率降低约85%,该试验结果与第一性原理计算的结果较为吻合。     

(Fe0.33Co0.33Ni0.33)84-xCr8Mn8Bx高熵非晶合金薄带的结构特征及其晶化行为

基于前期的研究结果,降低Mn和Cr元素的含量,将2者的原子分数均固定在8%,设计出(Fe_0.33Co_0.33Ni^0.33)_84-xCr₈Mn₈B_x(x=10、11、13、15和18)合金(简称10B、11B、13B、15B和18B),采用真空熔融甩带法制备出该系列合金的薄带。将合金薄带在不同温度下进行退火处理,通过XRD、DSC、TEM、SEM、万能拉伸试验机、OM、Vickers硬度计等研究了合金薄带的结构特征、晶化行为和力学性能。结果表明:11B合金薄带已完全形成非晶相(am),11B~18B合金薄带加热时都有2个结晶转变放热峰,B元素的添加提高了该系列合金的非晶形成能力(GFA)和热稳定性。11B~18B合金薄带在不同温度退火,bcc相、fcc相和硼化物(M₂₃B₆)等1种或多种混合物析出,其结晶行为分别为:11B和13B,[am]→[am′+bcc]→[am″+bcc+fcc]→[bcc+fcc+M₂₃B₆]→[fcc+M₂₃B₆];15B,[am]→[am′+fcc+bcc]→[am″+bcc+fcc+M₂₃B₆]→[bcc+fcc+M₂₃B₆]→[fcc+M₂₃B₆];18B,[am]→[am′+fcc]→[am″+fcc+M₂₃B₆]→[fcc+M₂₃B₆](其中,am′和am″分别为第1次和第2次结晶残余非晶相)。     

Cu-Ni-Sn三元系相平衡的热力学计算

基于Cu-Ni-Sn三元系的相平衡和热力学的实验信息,采用亚正规溶体模型描述液相和fcc相的Gibbs自由能,为了预测该体系中bcc相的A2-B2有序-无序转变,bcc相的Gibbs自由能采用双亚点阵模型进行描述.利用CALPHAD(相图计算)方法评估了Cu-Ni-Sn三元系各相的热力学参数,计算的富Cu侧相图和热力学性质与实验数据比较一致.并对该三元系中bcc相的A2-B2有序-无序转变及fcc相的溶解度间隙进行了计算.这些计算结果对利用析出强化以及Spinodal分解开发高强度和高导电性的新型Cu基合金的组织设计具有一定的指导意义.     

纳米晶和粗晶Fe-0.5Si合金的高温氧化行为

利用机械合金化方法制备了纳米晶(NC)Fe-0.5Si合金(质量百分数,下同),研究了该合金在900℃和1000℃流动纯氧气中的氧化行为,并与相同条件下利用电弧熔炼方法制备的粗晶(CG)Fe-0.5Si合金的氧化行为进行比较。两种Fe-Si合金都形成了类似的混合氧化物层结构(Fe2O3+Fe3O4+FeO+SiO2)。两个试验温度下,NC Fe-0.5Si表现出比CG Fe-0.5Si更快的氧化速度。这是由于NC Fe-0.5Si合金具有更多的晶界,促进了Fe向外扩散和氧向内扩散,从而使氧化速度明显提高。虽然NC Fe-0.5Si较CG Fe-0.5Si形成的混合氧化物层中SiO2的体积分数明显提高,但Fe和氧扩散的绝对速度仍然增大。纳米化降低了Fe-0.5Si合金的抗高温氧化性能。     

Fe-1C-xSi合金的液态结构

利用高温液态X射线衍射研究了纯铁，Fe-1C和Fe-1Si合金在约1550℃及Fe-1C-xSi(质量分数，％）合金从熔点附近至1560℃的液态结构。结果表明：与纯铁的最近邻距离r1=0.259nm和配位数N1＝10.5相比，液态Fe-1C合金的r1和N1略有增加。而液态Fe-1Si合金的r1和N1却略微减小。在1560－1470℃，液态Fe-1C-1Si合金的r1=0.254-0.250nm，明显低于液态Fe-1C合金和Fe-1Si合金的r1值。从1560℃降温至1530℃时，Fe-1C-1Si合金的r1值减少，而N1由10.3剧增至118.8，并且在熔点以上不高的温度保持12.0不变，分析表明：在液态二元系中，C和Si以不同形式存在；而在三元系中，C和Si对纯铁的液态结构具有复杂的影响。Fe-1C-1Si合金在1560－1530℃范围内存在由δ相向γ相的转变，而这种相变随Si含量的增加向低温区域扩展，在Si含量为4％时熔体为单一的δ相，这主要是Si元素抑制γ相区而扩展δ相区产生的。     

粉末冶金制备AlNiCrFeCuMo_x高熵合金及其性能(英文)

采用粉末冶金法制备AlNiCrFeCuMox(x=0～0.2)合金,研究Mo含量对合金微观组织以及力学性能的影响。随着Mo含量的增加,AlNiCrFeCuMox合金的微观组织均为典型的花瓣状枝晶,且由于高熵效应,使得体系的相组成十分简单,均为bcc和fcc;bcc最高峰的强度会逐渐降低,相应地fcc的强度有所增加,所以Mo元素促进了fcc结构的生成。同时,当x=0.1时,合金拥有较好的力学性能,硬度达到5160MPa,断裂强度为1161MPa,最大变形率为24.4%。AlNiCrFeCuMox合金的力学性能变化是元素性质与晶体结构综合作用的结果。     

Mn和Ce对Fe-Ni-Mn-C-Si-Ce系合金组织和性能的影响

采用熔炼法制备出新型高耐磨的Fe-20Ni-xMn-3.5C-2.5Si系固体自润滑材料,研究稀土元素Ce对Fe-20Ni-xMn-3.5C-2.5Si系合金中石墨的球化作用及Mn含量对力学性能及摩擦磨损性能的影响。结果表明：随着Mn含量的增加,合金凝固组织中奥氏体的硬度逐渐增大,特别是Fe-20Ni-xMn-3.5C-2.5Si-0.75Ce系合金在摩擦过程中的表面硬度大幅度提高,呈现出高锰钢特有的表面加工硬化性质,通过TEM可以观察到磨损表面生成孪晶型马氏体;添加0.75%（质量分数）的稀土Ce可以使结晶的石墨球化,使抗拉强度和抗弯强度大幅度提高,大约比未经球化处理的提高3～5.8倍;稀土Ce的加入可以促进Fe1.1Mn3.9C2型碳化物的生成,使材料的耐磨性进一步提高,其中Fe-20Ni-16Mn-3.5C-2.5Si-0.75Ce合金的磨损率最低,大约是QT500球墨铸铁的1/13。     

机械合金化诱导Fe—Cu系固溶度的扩展

X射线衍射(XRD)表明室温下几乎不固溶的Fe—Cu系经5h球磨后可形成亚稳过饱和固溶体.对于Fe_(1-x)Cu_x,当0≤x≤0.10时形成单一的bcc相,x≥0.30时形成单一的fcc相,0.10相似文献   

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。