Pd替代对Ti-Zr-Ni准晶合金中的相形成与稳定性影响（英文）EI北大核心CSCD

Pd能用来作为添加元素改善Ti-Zr-Ni准晶合金的吸氢性能,但是Pd添加的作用机制仍然不清楚。本工作通过采用XRD、TEM、DSC分析技术研究了Pd在Ti45Zr38Ni17和Ti40Zr40Ni20两个合金中对Ti、Zr的替代行为。结果显示：在前1个合金中,替代4%-6%（原子分数,下同）Ti或4%Zr能够确保纯二十面体准晶形成;在后一个合金中,替代3%-4%Ti或3%以下Zr才能形成纯二十面体准晶。这说明Ti具有更高的替代极限。Ti39Zr38Ni17Pd6与Ti36Zr40Ni20Pd4两个衍生准晶合金在400℃温度下退火会转变为晶体相,而它们的初始准晶合金Ti45Zr38Ni17和Ti40Zr40Ni20在400℃仍然结构稳定,这反映出添加Pd后准晶合金的热力学稳定性变低。这种替代趋势和准晶稳定性的降低很可能归功于Pd具有适宜的原子尺寸。     

塑性变形对Zr-Al-Ni-Cu-Ag非晶合金中二十面体准晶相析出的影响

利用x射线衍射(XRD)和差示扫描量热法(DSC)研究了轧制对Zr65Al7.5Ni10Cu12.5Ag5非晶合金中二十面体准晶相析出的影响.实验发现,经轧制塑性变形合金在随后的加热过程中二十面体准晶相的析出量增加,在变形量ε=70%时达到最大.另外,析出的二十面体准晶相的稳定性随着变形量增大而提高,在ε=70%时达到最大,随后又开始降低.这是由于合金在塑性变形过程中的原子组态发生变化所致.     

3D Morphology and Formation Process of the Icosahedral Quasicrystalline Phase in Rapidly Solidified Al-Mn Alloy

Three-dimensional morphology and formation process of icosahedral quasicrystal phase have been investigated in a melt-spun Al-18 Mn alloy(in wt%).Three distinct layers corresponding to varying temperature gradient have been observed on the cross section of the ribbons.3D morphologies of cellular and dendritic icosahedral phase have been obtained through electro-etching.A model has been proposed to describe the formation process of the icosahedral phase and α-Al during the rapid solidification.The icosahedral phases are primarily precipitated from the melt into fine cellular and dendritic particles,and subsequently engulfed by the α-Al which propagates in a planar morphology.     

Microstructure and mechanical properties of Mg-Zn-Gd-based alloys strengthened with quasicrystal and Laves phase

One kind of Mg3.5Zn0.6Gd-based alloy strengthened with quasicrystals was designed, and the effect of alloying elements on microstructure and mechanical properties of as-cast Mg-Zn-Gd alloy at room temperature and elevated temperatures were studied. The results indicate that MgZnCu Laves phase, which coexists with quasicrystal at grain boundary, emerges with the addition of copper element in Mg-Zn-Gd alloy. The strength of alloys exhibits the parabola curve with the increase of copper content. The alloy with 1.5% （mole fraction） Cu shows better mechanical properties at room temperature： tensile strength 176 MPa, yield strength 176 MPa and elongation 6.5%. The existence of MgZnCu Laves phase can effectively improve the heat resistance and elevated temperature properties of the alloy. The alloy with 1.5% Cu has better mechanical properties at 200℃ ： tensile strength 130 MPa and elongation 18.5%. The creep test of the alloys at 200℃ and 50 MPa for 102 h indicates that Mg3.5Zn0.6Gd alloy reinforced with quasicrystal has better creep properties than AE42, which can be further improved with the introduction of Laves phase in the alloy.     

Laves相金属间铬化物的制备研究进展

拓扑密排结构的金属间化合物是潜在的高温结构材料,Laves相金属间化合物是其中最大的一类。而Laves相金属间铬化物Cr2X(X为Ti、Nb、Ta、Zr、Hf等)近年来成为高温结构材料研究中的一个热点,因为这些化合物具有较高的熔点、较低的密度和比较好的抗氧化性。有多种方法可以制备Laves相金属间铬化物。对目前Laves相铬化物的各种制备工艺技术现状及研究进展进行了综述,重点介绍了国内外制备Laves相金属间铬化物的熔铸法、定向凝固、机械合金化(MA)、机械合金化 热固相反应、机械合金化 热压法及铸锭冶金等有效技术,并评述了这些制备工艺的优缺点,指出了研究中存在的问题和今后的发展方向。     

Phase Stability of the Laves Phase Cr2Nb in a Two-Phase Cr-Cr2Nb Alloy

The phase stability of the Laves phase Cr2Nb in a two-phase Cr-Cr2Nb alloy produced by arc-melting was investigated using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The experimental results indicated that the as-cast ingot was consisted of C15-Cr2Nb and Cr phases; the intermediate C36 and high-temperature C14 modifications of Cr2Nb, reported in literatures, were not detected in this study. These results, combined with a detailed analysis of the actual solidification conditions, revealed that the C14-Cr2Nb was a metastable rather than a stable high-temperature modification. Moreover, a kind of extremely fine lamellar structure was found to be randomly distributed in the eutectic cells, which may be formed by decomposition of the supersaturated C15-Cr2Nb via a discontinuous precipitation reaction.     

熔体快淬对AB2型Laves相储氢电极合金循环寿命的影响

研究了快淬处理对AB2型Laves相电极合金循环稳定性的影响，用XRD和SEM分析了铸态及快淬态合金的相结构，并观察了合金的微观组织形貌。结果表明，快淬对AB2型贮氢合金循环稳定性的影响与合金的成分密切相关。快淬对Ti基电极合金的循环寿命有所提高，但不显著；对Ti—Zr基合金，随淬速增加，合金的循环稳定性急剧增加。快淬使AB2型电极合金循环寿命发生变化的根本原因是合金中形成了不同量的非晶相。     

Laves相铬化物高温抗氧化性能的研究进展

Laves相铬化物以其熔点高、适当的密度和良好的高温强度成为重要的潜在高温结构材料，但高温抗氧化性能较差是制约其应用的关键问题之一。从Laves相铬化物的氧化机理、合金化抗氧化保护和表面涂层保护三方面，阐述了Laves相铬化物高温抗氧化的研究进展，分析了研究中面临的问题，并提出了解决的途径。     

Al-Cu-Co十次准晶颗粒增强铝基复合材料的微观组织和制备中的相转变

采用电弧炉熔炼配置成分为Al65Cu15Co20十次准晶合金锭,并以Al65Cu15Co20准晶颗粒为增强相,Al-4.5%Cu合金为基体,采用熔体机械搅拌法制备准晶颗粒增强铝基复合材料.利用XRD、SEM及EDS分析Al65Cu15Co20准晶合金及颗粒增强铝基复合材料的相成分、微观组织及各组成相的分布,并详细分析准晶颗粒加入熔体前后的形貌、相成分和结构的变化.由于准晶颗粒与熔体之间的相互扩散作用,使得准晶颗粒加入熔体后迅速失稳,其形貌则由加入前的不规则多边形状转变成块状和板条状,并发生如下相转变:D-Al62.10Cu17.46Co20.44→θ-Al79.58Cu1.10Co19.32,在随后的凝固过程中,由于"界面推移效应"使得θ相沿晶界处均匀分布.     

铸态Ti-Zr-(Ni,Co)伪三元准晶合金研究

沿Ti9(Ni，Co)4-Zr变电子浓度线设计系列合金成分．用吸铸方法可制备出Ti-Zr-(Ni，Co)准晶，其中Ti42Zr40(Ni，Co)18为形成准晶的最佳成分点，Ti-Zr-(Ni，Co)伪三元准晶系列的准点阵常数介于0．506～0．518nm之间。实验结果表明，Co是形成准晶的不利组元，其含量的增加将促使Ti2Ni、fcc-Zr2Ni和β-Zr(Ti)固溶相的形成，使合金中准晶相的含量大为降低；但适量Si的加入(～2at％)能促进Ti-Zr-(Ni，Co)准晶的形成。     

Laves Phase Formation and Its Effect on Mechanical Properties in P91 Steel

Effect of Laves phase formation on mechanical properties in a pressurized T-junction of P91 steel pipe at849 K for 58,000 h with 25.65 MPa vapor pressure was studied. Thermodynamic calculations had been performed by using the software Thermo-Calc to study the phase at equilibrium state. Counter plot of von Mises stress in the pipe during service life was calculated by finite element analysis to study the effect of the operated stress distribution on the evolution of Laves phase. The change in the microstructure and mechanical properties in the sites with different stress was also studied. The results indicated that the formation of Laves phase in P91 steel was a thermodynamically possible process due to enrichment of Mo and depletion of C adjacent to M23C6 particles or along martensite lath and packet boundaries. The formation of Laves phase had a detrimental influence on the mechanical properties in P91 steel. The mean size of Laves phase would be significantly increased with increasing operated stress, leading to a reduction in tensile properties and impact energy. In particular, crack initiation energy and crack growth energy during impact test rapidly decreased with increasing the mean size and volume fraction of Laves phase.     

Precipitate Phases in an 11% Cr Ferritic/Martensitic Steel with Tempering and Creep Conditions

Precipitates in an 11% Cr ferritic/martensitic steel containing Nd with tempering and creep conditions were investigated using transmission electron microscope with energy-dispersive X-ray spectroscopy. The precipitates in the steel with a tempering condition were identified to be Cr-rich M23C6 carbide, Nb-rich/V-rich/Ta–Nb-rich MX carbides, Nbrich MX carbonitride, and Fe-rich M5C2 carbide. Nd-rich carbonitride, which is not known to have been reported previously in steels, was also detected in the steel after tempering. Most of the Nb-rich MX precipitates were dissolved, whereas the amount of Ta-rich MX precipitates was increased significantly in the steel after a creep test at 600 °C at an applied stress of180 MPa for 1,100 h. No Fe2 W Laves phase has been detected in the steel after tempering.(Fe, Cr)2W Laves phase with a relatively large size was observed in the steel after the creep test.     

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 采用化学定量相分析技术并借助于光学显微镜、XRD、SEM、TEM及常规的力学检测设备,研究了600 ℃下P92钢中Laves相对强度的影响规律,结果表明：Laves相在时效过程中析出,时效时间在100 h 内, Laves相快速形核, 1 000 h内,随着时效时间的延长,钢中Laves相含量逐渐增加并能有效提高P92钢室温和600 ℃高温强度;600 ℃下3 000 h内提高P92钢中狂钨、钼含量,增加Laves相的析出量,能够显著提高P92钢持久强度。     

AB2型Laves相贮氢合金的研究进展

文章主要综述了AB2型Laves相贮氢合金的种类及性能特点以及合金化及制备工艺对合金电化学性能的影响。介绍了AB2型Laves相贮氢合金研究的国内外动态及目前达到的水平,对AB2型Laves相贮氢合金未来的研究重点及发展方向提出了看法。     

Al72Ni12Co16准晶颗粒/铝基复合材料中的相转变及其力学性能

以Al72Ni12Co16单相十次准晶为增强颗粒、纯铝和Al-5.5%Zn（质量分数,下同）为基体制备铝基复合材料。采用扫描电镜和能谱分析复合材料的微观组织和颗粒分布情况。结果表明,准晶颗粒在熔体中热稳定性差而发生相转变。θ相呈规则的多变形状分布于Al基体中,颗粒尺寸主要在3.45~40 μm范围内分布;与此同时,晶界处还会形成细小的长条状γ相,其尺寸为1.15~8.57 μm。力学性能结果表明,最终形成的晶化相有助于提高复合材料的屈服强度、抗拉强度和弹性模量,而延伸率则急剧降低。     

Precipitation Behavior of Laves Phase in the Vicinity of Oxide Film of Ferritic Stainless Steel: Selective Oxidation-Induced Precipitation

Oxidation of Metals - Anti-corrosion behavior of Fe–Cr alloys at elevated temperature is greatly influenced by the protective nature of oxide scale formed on them. However, precipitates...     

Laves相NbCr2室温脆性的研究进展

对Laves相NbCr2及其室温脆性的研究进展进行了综合评述，着重介绍了Laves相NbCr2室温致脆的机理及提高其韧性的几种方法，包括细化晶粒、合金化和第二相增韧等，并就目前研究进展中的不足以及今后发展方向提出了一些看法。     

Laves相Ti36Zr40Ni20Pd4合金的吸氘行为

针对Ti36Zr40Ni20Pd4合金用X射线衍射仪和气固反应系统研究了其吸铸之前的晶体结构与吸氘特性。结果表明,吸铸前Ti36Zr40Ni20Pd4合金母锭形成了配位数为14的MgZn2结构的简单六方C14Laves相,晶格常数a=0.5287nm与c=0.8610nm。简单活化后,该合金可在室温下大量吸氘,浓度达到10.96mmol·D2/g·M(D2指氘分子,M指合金)。经过一次吸放氘循环后,吸氘动力学显著提高,吸氘速率常数达到0.015s-1。相对于成分相同的准晶相,Laves相Ti36Zr40Ni20Pd4合金吸氘较慢,但吸氘量相近,具有一定的储氢前景。     

二元合金Laves相结构的PLS分析

运用模式识别的偏最小二乘法(PLS)对AB2合金MgCu2型(C15)和MgZn2型(C14)Laves相进行研究,得出了影响二元合金Laves相结构的判据．对于由非过渡一过渡元素、过渡一过渡元素组成的合金,价电子密度是影响其Laves相结构的主要原因;对过渡一镧系(锕系)元素组成的合金,B原子的价电子数对其Laves相结构影响最为明显,且价电子和原子半径对Laves相结构的影响作用互为反向．     

Ni含量对MgCu2型Laves相的结构和力学性能影响

采用机械活化+热压烧结制备Laves相Mg(Cu1-xNix)2(0≤x≤0.35),对热压产物进行物相、显微组织及力学性能分析。结果表明:MgCu2中的部分Cu被Ni替代,晶体结构并未改变,主相仍为C15结构的Laves相。随Ni替代量增多,整个XRD衍射峰向高角度偏移量增大,点阵常数减小;Ni加入使组织均匀、细小,晶格畸变和晶粒尺寸增大,致密度提高,显微硬度增大,抗压强度和抗弯强度先增大后减小。