Cu-Zr-Ti系Cu基块体非晶合金的形成和成分优化

利用与团簇相关的变电子浓度判据研究了过渡金属Cu-Zr-Ti系中Cu基块体非晶合金的形成区域和成分特征.据此判据在Cu-Zr-Ti系相图中确定出三条特殊的成分线，(Cu_9／13Zr_4／13)_100-xTi_x，(Cu_0.618Zr_0.382)_100-xTi_x和(Cu_0.56Zr_0.44)关键词： 块体非晶合金 Cu-Zr-Ti合金 原子团簇 电子浓度     

粉末状态对激光立体成形Zr55Cu30Al10Ni5块体非晶合金晶化行为的影响

基于金属熔体结构的遗传性, 激光熔池的快速熔凝导致粉末的晶化状态可能会对最终成形件的晶化产生重要影响, 理清其影响规律对于制备大块非晶合金具有重要意义. 本文选取等离子旋转电极法所制粉末和1000 K退火态粉末为沉积材料, 采用激光立体成形技术沉积Zr₅₅Cu₃₀Al₁₀Ni₅块体非晶合金, 考察了粉末中已有晶化相对熔池及热影响区晶化行为的影响. 结果发现, 原始粉末组织由非晶相及粗大的Al₅Ni₃Zr₂相组成; 当激光线能量较低时, 相应熔覆层的熔池和热影响区皆含有Al₅Ni₃Zr₂相; 随着线能量的提高, 熔池中Al₅Ni₃Zr₂相消失, 保持了非晶态, 但热影响区晶化加重, 并有大量Al₅Ni₃Zr₂相析出; 当采用退火态粉末时, 即使线能量较小, 相应熔覆层仍主要由非晶构成, 几乎无Al₅Ni₃Zr₂相析出. 这是由于原始粉末在退火时其微观结构发生重排, 与Al₅Ni₃Zr₂相关的原子短程/中程有序结构减少, 导致已沉积层非晶区的热稳定性提高, 不利于Al₅Ni₃Zr₂相析出. 可见, 提高线能量将会加剧非晶沉积体的晶化, 而粉末中的Al₅Ni₃Zr₂团簇相状态对Zr₅₅Cu₃₀Al₁₀Ni₅合金沉积层的晶化有重要影响.     

Cu60Zr30Ti10非晶合金弛豫和晶化过程的小角X射线散射研究

应用小角X射线散射技术研究了Cu₆₀Zr₃₀Ti₁₀非晶合金从300到813 K之间微结构的演化情况.发现在淬火状态下Cu₆₀Zr₃₀Ti₁₀非晶合金中存在直径30 nm左右的富Cu区.非晶的结构弛豫包括573 K之前的低温结构弛豫和573 K到玻璃转变温度的高温结构弛豫，弛豫的结果是产生含有有序原子团簇的富Cu区，这些有序原子团簇的富Cu区是随后晶化过程中晶核产生的基础.Porod曲线分析表明，晶化生成的纳米体心立方CuZr相和基体之间有明锐的界面. 关键词： 小角X射线散射 非晶合金 结构弛豫 晶化     

Zr-Cu-Ni-Al-Nb大块非晶合金的晶化行为、力学性能及电化学腐蚀行为的研究

利用水冷铜模铸造法成功制备了Zr_65-xCu_17.5Al_7.5Ni ₁₀Nb_x (x=0，2，5)大块非晶合金. X射线衍射、热分析研究结果表 明，Nb的添加显著改变了非晶合金的晶化行为，促进了二十面体准晶相的形成. 各合金的准 静态压缩实验表明，Nb的适量添加有利于提高大块非晶合金的强度和塑性. 其中x=5的大块 非晶合金的抗压强度σ_b和塑性应变量ε_p 关键词： Zr基大块非晶合金 晶化行为 力学性能 耐腐蚀性能     

Nb添加对Cu-Zr非晶合金玻璃转变和晶化动力学的影响

采用铜模吸铸法制备出直径为2 mm的Cu_50.3Zr_49.7-xNb_x(x=0,2)大块非晶合金，利用示差扫描量热分析(DSC)研究了2at%Nb元素添加对Cu-Zr非晶合金玻璃转变动力学和晶化动力学的影响，发现含Nb合金具有较低的脆性指数，和较高的晶化激活能.这表明微量Nb的添加提高了该二元Cu基非晶合金过冷金属液相的热稳定性，从而有利于其非晶合金的形成. 关键词： Cu-Zr非晶合金 Nb添加 玻璃转变动力学 晶化动力学     

La基非晶合金β弛豫行为:退火和加载应变的影响

β弛豫行为是理解非晶合金扩散、塑性变形和玻璃转变行为的重要切入口.本研究以具有显著β弛豫行为的(La_0.6Ce_0.4)₆₅Al₁₀Co₂₅非晶合金为研究载体,利用动态力学分析仪,研究了加载频率、退火以及加载应变等因素对非晶合金β弛豫行为的影响.结果表明,随着加载频率的升高,非晶合金β弛豫峰向高温段移动.低于玻璃转变温度退火导致非晶合金β弛豫峰内耗值降低,非晶合金“缺陷”浓度降低,玻璃体系向更稳定状态迁移.随加载应变幅值增大,非晶合金β弛豫强度增大.本研究为进一步厘清非晶合金β弛豫起源提供新思路.     

Ni-Zr非晶合金晶化的透射电子显微镜研究(Ⅰ) ——Ni67Zr33晶化过程中的亚稳相

利用透射电子显微镜对Ni₆₇Zr₃₃非晶合金晶化的研究发现了两个新的亚稳相T₀与T₁0。其中T₁相为体心正交(准四方〕晶体,点阵常数a≌b=0.89nm,c=3.14nm,空间群为Iba2或Ibam。温度升高,T₁相转变为含有大量错排的A心正交Ni₁₀Zr₂相,用1/2(a+b)位移错排模型可以圆满地解释其电子衍射图中仅h+k为奇数的衍射斑沿c^*方向拉长的现象,晶化稳定相为Ni₁₀Zr,与Ni₂₁Zr₈(Ni₅Zr₂)相。 关键词：     

非晶态Fe90-xMnxZr10合金的磁性

本文报道用单辊急冷方法制备的非晶态合金Fe_90-xMn_xZr₁₀(x=0,4,6,10,15)的磁性,讨论了样品中每个原子的平均磁矩和居里温度T_c随Mn含量x的变化以及类自旋玻璃特性,给出了非晶态Fe_90-xMn_xZr₁₀合金的磁相图。观察到非晶态Fe₈₄Mn₆Zr₁₀合金晶化后的热磁曲线 关键词：     

a—Fe—(Co,Cr)—Zr系列合金的穆斯堡尔谱研究

本文研究了a-Fe_90-xCo_xZr₁₀(x=4,10,20,…,70)和Fe_90-yCr_yZr₁₀(y=0,4,7,16,20)系列合金的M?ssbaner谱。实验结果表明a-Fe_90-yCo_yZr₁₀和富Fe区(x<30)的a-Fe_90-xCo_xZr_{10 关键词：}     

非晶态Cu56Zr44合金的结构及其等温退火晶化过程的研究

利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu₅₆Zr₄₄合金的结构及其等温退火条件下的晶化过程.实验结果表明,非晶态Cu₅₆Zr₄₄合金在室温下的短程结构类似于硬球无规密堆积分布.在703K过冷液相区内等温退火时发现,当退火时间为3min时,晶化产物主要为Cu₈Zr₃相;当退火时间为6min时,Cu₈Zr₃关键词： 非晶态 56Zr₄₄合金')" href="#">Cu₅₆Zr₄₄合金 结构 等温退火     

Heredity of clusters in the rapidly cooling processes of Al-doped Zr_(50)Cu_(50) melts and its correlation with the glass-forming ability

The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA) are studied via molecular dynamics simulations. Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_x systems. The [12/555] icosahedra and their medium-range order(IMRO) play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_x metallic glasses(MGs). The fraction of [12/555], the number of IMRO, and the maximum size of IMRO in MGs increase significantly with increasing x. A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity. Instead, a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50) alloys.     

Novel structures and mechanical properties of Zr_2N:Ab initio description under high pressures

With the formation of structural vacancies,zirconium nitrides(key materials for cutting coatings,super wearresistance,and thermal barrier coatings) display a variety of compositions and phases featuring both cation and nitrogen enrichment.This study presents a systematic exploration of the stable crystal structures of zirconium heminitride combining the evolutionary algorithm method and ab initio density functional theory calculations at pressures of 0 GPa,30 GPa,60 GPa,90 GPa,120 GPa,150 GPa,and 200 GPa.In addition to the previously proposed phases P42/mnm-,Pnnn-,and Cmcm-Zr2 N,five new high-pressure Zr₂N phases of PA/nmm,IA/mcm,P2₁/m,P3 m1,and C2/m are discovered.An enthalpy study of these candidate configurations reveals various structural phase transformations of Zr2 N under pressure.By calculating the elastic constants and phonon dispersion,the mechanical and dynamical stabilities of all predicted structures are examined at ambient and high pressures.To understand the structure-property relationships,the mechanical properties of all Zr₂N compounds are investigated,including the elastic moduli,Vickers hardness,and directional dependence of Young’s modulus.The Cmncm-Zr2 N phase is found to belong to the brittle materials and has the highest Vickers hardness(12.9 GPa) among all candidate phases,while the I4/mcm-Zr2 N phase is the most ductile and has the lowest Vickers hardness(2.1 GPa).Furthermore,the electronic mechanism underlying the diverse mechanical behaviors of Zr2 N structures is discussed by analyzing the partial density of states.     

An Attempt to Prepare Metallic Glasses from Quasicrystals

Icosahedrons in supercooled liquids and glasses are considered to be of significance for the glass formation in alloy systems.Starting from the similarity of the local structure of quasicrystals to the icosahedrons in metallic glasses,a scheme is put forward to prepare metallic glasses based on a well-known quasicrystal Zr_(40)Ti_(40)Ni_(20).A series of(Zr_(40)Ti_(40)Ni_(20))_(100-x)Co_x metallic glasses are fabricated,and the optimized glass forming composition is determined at(Zr_(40)Ti_(40)Ni_(20))_(92)Co_8.The results show that the glass-forming ability of the alloys is closely related to the quasicrystalline phases.The mechanism of the enhanced glass-forming ability is discussed.     

Low thermal expansion and broad band photoluminescence of Zr0.1Al1.9Mo2.9V0.1O12

A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices.     

Imaging the diffusion pathway of Al~(3+) ion in NASICON-type(Al_(0.2)Zr_(0.8))_(20/19)Nb(PO_4)_3 as electrolyte for rechargeable solid-state Al batteries

Among all-solid-state batteries, rechargeable Al-ion batteries have attracted most attention because they involve threeelectron-redox reactions with high theoretic specific capacity. However, the solid Al-ion conductor electrolytes are less studied. Here, the microscopic path of Al~(3+)-ion conduction of NASICON-type(Al_(0.2)Zr_(0.8))_(20/19)Nb(PO_4)_3 oxide is identified by temperature-dependent neutron powder diffraction and aberration-corrected scanning transmission electron microscopy experiments.(Al_(0.2) Zr_(0.8))_(20/19) Nb(PO_4)_3 shows a rhombohedral structure consisting of a framework of(Zr,Nb)O_6 octahedra sharing corners with(PO_4) tetrahedra; the Al occupy trigonal antiprisms exhibiting extremely large displacement factors. This suggests a strong displacement of Al ions along the c axis of the unit cell as they diffuse across the structure by a vacancy mechanism. Negative thermal expansion behavior is also identified along a and b axes, due to folding of the framework as temperature increases.     

High-throughput screening for biomedical applications in a Ti-Zr-Nb alloy system through masking co-sputtering

A method of co-sputtering deposition combined with physical masking was applied to the parallel preparation of a ternary Ti-NbZr system alloy. Sixteen independent specimens with varying compositions were obtained. Their microstructure, phase structure,Young's modulus, nanoindentation hardness, and electrochemical behavior in a phosphate buffer solution(PBS) were studied in detail. It was revealed that the Ti-Zr-Nb alloys possess a single BCC structure. As confirmed via nanoindentation tests, the Young's modulus of the specimens ranged from 80.3 to 94.8 GPa and the nanoindentation hardness ranged from 3.6 to 5.0 GPa.By optimizing the composition of the specimens, the Ti_(34)Zr_(52)Nb_(14) alloy was made to possess the lowest modulus in this work(76.5 GPa). Moreover, the Ti_(34)Zr_(52)Nb_(14) alloy showed excellent corrosion resistance in PBS without any tendency for pitting at anodic potentials up to 1 Vsce. These preliminary advantages offer the opportunity to explore new orthopedic implant alloys based on Ti-Zr-Nb alloys. Moreover, this work provides an effective method for the parallel preparation of biomedical alloys.     

Phase and structural transformations in a molecular dynamics model of iron under ultrafast heating and cooling

It is shown that a system of classical particles considered in a molecular dynamics model with Pak-Doyama pairwise interatomic potential adequately describes not only the various structural states of iron (melt, bcc crystal, metal glass) but also the complex self-organization processes occurring in first-and second-order phase transitions (crystallization and vitrification, respectively). When the temperature is varied at a constant rate of 6.6×10¹¹ K/s, crystallization sets in from both the amorphous and the liquid state; at a rate of 1.9×10¹² K/s, crystallization is observed only in the amorphous state; and when heated at a rate of 4.4×10¹² K/s, the model amorphous iron transfers to the liquid state without crystallization. The energy of homogeneous formation of a crystal nucleus in the bulk of the amorphous phase of iron is calculated to be ～0.71 eV under the assumption that there is a spectrum of activation energies.     

Vanillin Phosphorescence as a Probe of Molecular Mobility in Amorphous Sucrose

Changes in molecular mobility are important in defining the stability and quality of amorphous solid foods, pharmaceuticals, and other solid biomaterials. Predictions of stability must consider matrix mobility below and above T_g (the glass transition temperature); measurement of molecular mobility in amorphous solids over time scales ranging from <10⁻⁹ s to >10⁸ s requires specialized methods. This research investigated how the steady-state and time-resolved emission and intensity of phosphorescence from vanillin (4-hydroxy-3-methoxy benzaldehyde), a common flavor compound, can be used to probe molecular mobility when dispersed within amorphous pure sucrose films. Phosphorescence emission spectra and time-resolved intensity decays, measured in sucrose as a function of temperature in the absence of oxygen, were strongly modulated by matrix molecular mobility. Temperature had a significant effect on vanillin phosphorescence peak frequency and bandwidth, intensity, and lifetime both in the glass and in the melt. Time-resolved phosphorescence intensity decays from vanillin were multiexponential both below and above the glass transition temperature, indicating that the pure (single component) amorphous matrix was dynamically heterogeneous on the molecular level. These data show that vanillin is a promising intrinsic probe of molecular mobility and dynamic heterogeneity in amorphous solid foods and perhaps pharmaceuticals.