X-ray studies of structure defects in nanostructured FeAl alloy

The evolution of the microstructure of the mixture iron and aluminium powders during the high energy mechanical alloying process was investigated by X-ray line profile analysis. Analysis of line breadths was carried out to get an insight into the interrelated effects of grain size, lattice strain and dislocations. The final product of the MA process was the nanocrystalline Fe(Al) solid solution with a mean crystallite of 10 nm. On the basic on the modified Williamson-Hall plots, the root-mean squared strains were explained by the presence of dislocations, with a dislocation density of about 6 × 10¹⁶ m^− 2. The identified steady-state saturation values of these parameters can be related to accumulate strain hardening of the powder material during longer milling times.     

机械合金化Fe-Ni粉末的相结构

使用XRD和Moessbauer等方法，研究了在Ar气氛下机械合金化Fe—Ni粉末相结构的变化．结果表明，在机械合金化Fe64-Ni36粉末过程中，fcc相的数量随着球磨时间的增加先增加然后减少，与加乙醇球磨Fe64-Ni36的情形相同．当Ni的含量(原子分数)大于50％时，有fcc相、顺磁相和FeNi3形成，当Ni的含量低于50％时，bcc相的数量随着Ni含量减少而增加．Moessbauer谱的结果表明，因球磨时间或Fe、Ni比例的不同，Fe—Ni球磨粉末固溶体具有不同结构的原子配比。     

Capability of mechanical alloying and SPS technique to develop nanostructured high Cr,Al alloyed ODS steels

Abstract

Oxide dispersion strengthened (ODS) Fe alloys were produced by mechanical alloying (MA) with the aim of developing a nanostructured powder. The milled powders were consolidated by spark plasma sintering (SPS). Two prealloyed high chromium stainless steels (Fe–14Cr–5Al–3W) and (Fe–20Cr–5Al+3W) with additions of Y₂O₃ and Ti powders are densified to evaluate the influence of the powder composition on mechanical properties. The microstructure was characterised by scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) was used to analyse grain orientation, grain boundary geometries and distribution grain size. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) equipped with energy dispersive X-ray spectrometer (EDX) were used to observe the nanostructure of ODS alloys and especially to observe and analyse the nanoprecipitates. Vickers microhardness and tensile tests (in situ and ex situ) have been performed on the ODS alloys developed in this work.     

聚吡咯网状纳米结构的合成及表征

采用原位聚合法,以聚乙二醇-6000(PEG-6000)为表面活性剂合成网状纳米聚吡咯(PPy),并考察了反应物的物质的量比对产品的形貌和吸波性能影响。利用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、矢量网络分析仪对其进行表征,结果表明,Py∶HCl∶FeCl3物质的量比为1∶0.5∶2时,聚吡咯的吸波性能最佳,在3430MHz处达到了-38.9dB。     

High temperature magnetic properties of mechanically alloyed Fe–Zr powder

We report the preparation and characterization of amorphous/non-equilibrium solid solution Fe_100 − xZr_x (x = 20–35) alloys by mechanical alloying process. The microstructure and magnetic properties of milled powders have been studied as a function of Zr substitution. The effective magnetic moment of as-milled powders decreases as concentration of Zr is increased. Thermomagnetization measurements confirmed that the Fe₈₀Zr₂₀ sample exhibits two clear magnetic phase transitions due to the co-existence of an amorphous phase and a Fe rich non-equilibrium solid solution. All the other samples exhibiting an amorphous structure showed a single magnetic phase transition with Curie temperature of ~ 570 °C,which did not vary much with different composition. The Curie temperature of the mechanically alloyed powders is noticeably higher than those of melt-spun amorphous ribbons.     

Synthesis and characterization of nanostructured silicon carbide

Equiatomic nanostructured silicon carbide was successfully prepared by milling elemental Si and C powders, using a planetary ball mill. The synthesis of this carbide proceeded at milling conditions corresponding to 5.19 W/g shock power. The reaction was gradual and completed after 15 h. After 20 h of alloying duration and towards the end of the process, the SiC diffraction crystallite size (DCS) reached a critical value of 4 nm. At this same alloying duration, SEM characterization revealed that the powders exhibit homogeneous distribution of the particles with 0.3 µm in size.     

硬质相对冷喷涂FeAl金属间化合物涂层性能的影响

FeAl金属间化合物具有优良的物理性能和力学性能,但其室温塑性和断裂韧性低,限制了其工程应用.利用机械合金化制备了Fe(Al)固溶体合金粉末及Al2O3,WC硬质相增强的复合合金粉末,通过冷喷涂沉积涂层并结合后热处理原位反应制备了FeAl金属间化合物涂层及其复合涂层.利用扫描电镜(SEM)、X射线衍射仪(XRD)及显微硬度仪等研究了硬质相对球磨粉末组织结构、冷喷涂FeAl金属间化合物涂层组织结构及性能的影响.结果表明.硬质相可显著加速球磨粉末内部层状结构的细化程度,喷涂态涂层具有不同于传统热喷涂涂层的层状组织结构,热处理可实现喷涂态涂层中Fe(Al)固溶体向FeAl金属间化合物的原位转变,致使层状结构消失,获得无粒子界面的FeAl金属间化合物涂层,弥散分布的硬质相可显著提高冷喷涂FeAl金属间化合物涂层的强化稳定性.     

Consolidation of mechanically alloyed powder mixture of Cu–Zn alloy and graphite

A powder mixture consisting of Cu–29.7at.% Zn alloy and graphite was mechanically alloyed in a planetary ball mill. The supersaturated solid solubility of carbon in the Cu–29.7at.% Zn alloy was determined to be 38.5at.% C (alloy composition: Cu–18.3at.% Zn–38.5at.% C) by the change in lattice parameter of the alloy. Supersaturated Cu–24.2at.% Zn–18.5at.% C alloy powder consolidated by a static compression stress of 1.4 GPa was found to have a relative density of 89.7%, a Vickers hardness of 147.2, and a compressive strength of 1.4 GPa which is equal to the statically consolidated compression stress. Moreover, the supersaturated solid-soluble carbon did not precipitate. When dynamically consolidated by a 93 g projectile at a speed of 38.1 m s⁻¹ (estimated impact compression stress of 2.3 GPa) after static precompression of 0.4 GPa, the alloy powder was found to have a relative density of 93%, a Vickers hardness of 177, and a compressive strength of 2.3 GPa which is equal to the impact compression stress. Supersaturated solid solubility of 18.5at.% C decreased to 15at.% C after impact consolidation. The mechanically alloyed powders can maintain supersaturated solid solubility when consolidated by impact pressure, and especially when consolidated by static pressure.     

FeAl金属间化合物的高温变形行为

对Ｆｅ－３６．５ａｔ％Ａｌ金属间化合物进行了高温拉伸试验研究。结果表明，变形温度在６００－１０００℃范围内，这种ＦｅＡｌ合金的延伸率随温度的升高不断增加，在１０００℃时延伸率最高，达１１５％。经透射电镜分析，该合金高温变形后不仅有大量的滑移位错线，而且有一定数量的位错绻线存在。     

Synthesis and process characterization of mechanically alloyed icosahedral phase Mg-Zn-Al

The formation process of the icosahedral i-Mg₃₂ (Zn, Al)₄₉ phase during mechanical alloying has been studied. In the case of synthesis of i-phase from the metal powder mixture, the intermediate amorphous phase appeared during the first stages of mechanical alloying. In contrast the transformation of the cubic Frank-Kasper phase into the icosahedral one, was accompanied by progressive broadening and disappearance of the Bragg's peaks of the cubic phase without amorphization. These observations are discussed in terms of the structural relations of the amorphous, icosahedral and cubic Frank-Kasper phases, the formation and packing of icosahedral clusters during mechanical alloying of the metal powder mixtures and, on the other hand, the distortion of the cubic phase due to the formation of line defects.     

过程控制剂对机械合金化Fe-48Al粉末特性的影响

研究了过程控制剂(PCA)-无水乙醇和硬脂酸对机械合金化Fe-48Al(Al原子分数为48%,下同)粉末特性的影响.利用激光粒度仪、扫描电镜和X射线衍射仪分别研究了球磨粉末的粒度、形貌和热处理前后物相结构的变化规律.结果表明,以无水乙醇作PCA时,Fe-48Al的机械合金化速度较快,粉末粒度较小呈不规则薄片状;以硬脂酸作PCA则有利于球磨粉末形态向厚片状或近球形转化.两种粉末经12h球磨后,仍保持固溶体结构;经1100℃真空热处理后,两者均可转变为FeAl(B2)金属间化合物,但无水乙醇作PCA的球磨粉末中Al2O3生成量相对较多.     

Micromechanical characterization of bulk composite prepared by sintering of mechanically alloyed aluminum-316 stainless steel (35 wt%) powder blend

Present study concerns deformation behavior of the ball milled and consolidated powder blend comprising 316 stainless steel and elemental Al (65 wt%), studied by the micro- and nano-indentation techniques. With an aim to examine the strain hardening behavior of the consolidated samples, nano-indentation measurements have been carried out by applying variable load at multiple spots and cyclic load at the single spot. Similar experiments have been carried out for the bulk 316-stainless steel plate to compare the results with those obtained from the consolidated samples. The consolidated samples exhibited much higher hardness values than the plate along with high elastic recovery and appreciable work hardening.     

(FeAl)_(1-x)Ni_x和(FeAl_3)_(1-x)Ni_x机械合金化研究

为了研究按摩尔分数(FeAl)1-xNix(x=0.4,0.6)和(FeAl3)1-xNi(x=0.1,0.3)配比的粉体在机械合金化过程中的结构演变,采用X射线衍射(XRD)对球磨样品进行分析。结果表明:球磨50h后的产物主要由Fe和Al的原子比来决定,Ni的成分含量大小对主要产物基本没有影响。     

粉末粒度对FeAl金属间化合物多孔材料孔结构的影响

研究了粉末粒度对FeAl金属间化合物多孔材料孔结构的影响.研究表明,当粉末粒径在60μm以上时,随着粉末粒径的增加,FeAl金属间化合物多孔材料的总孔隙度和开孔隙度变化不大,即粉末粒度不是决定FeAl多孔材料孔隙度的主要因素;粉末粒度是决定FeAl金属间化合物多孔材料最大孔径的主要因素,在18～125μm的粒度范围内,多孔体最大孔径与粉末粒径之间严格遵循dm=0.4·d.的直线变化规律.     

喷射-沉淀法合成纳米晶Ni-Zn铁氧体及表征

采用喷射-沉淀法成功地制备了纳米晶Ni-Zn铁氧体粉料。通过XRD、TG．DSC、SEM、TEM和BET等测试手段分析了其微观结构和形貌．结果表明：沉淀剂种类和溶液pH值对喷射．共沉淀法制备Ni-zn铁氧体纳米粉的物相和结构有着显著影响。采用NaOH溶液为沉淀剂，pH值范围为7．0～7．5，可以获得颗粒细小均匀、形状完整的纳米晶Ni-Zn铁氧体粉料。在600℃煅烧1．5h，样品晶粒尺寸为30nm左右，平均颗粒尺寸小于100nm。     

Morphology,structure, and chemistry of nanoclusters in a mechanically alloyed nanostructured ferritic steel

Nanostructured ferritic steels have excellent elevated temperature strengths, creep resistances, and radiation tolerances due to the presence of a high density of Ti–Y–O-enriched nanoclusters. The compositions, morphologies, and structures of the smallest of these nanoclusters with maximum dimensions of ~2–4 nm were investigated in alloy 14YWT by high-resolution scanning transmission electron microscopy and atom probe tomography. Nanoclusters are found to be coherent with truncated rhombic dodecahedron morphologies defined by the {100} and {110} planes in the Fe matrix. Particles have compositions rich in Ti, O, Y, and Cr that are inconsistent with known oxide structures. The smallest nanoclusters appear to lack an identifiable crystal structure. Both nano-diffraction and focal series imaging through the sample thickness suggest that they are amorphous.     

Crystallization kinetics of mechanically alloyed amorphous Fe-Ti alloys during annealing

The crystallization behaviors of mechanically alloyed amorphous Fe-Ti alloys were studied. The α-Fe phase formed during annealing as a result of the devitrification of the amorphous phase. According to the Kissinger plot, the crystallization activation energy (E) was obtained as 171 kJ/mol, which is close to the activation energy for the diffusion of Fe in α-Ti. According to the non-isothermal Johnson–Mehl–Avrami (JMA) analysis and obtaining the volume fraction of the crystalline phase from the differential scanning calorimetry (DSC) plots, the average Avrami exponent (n) was determined as 1.61 and 5.67 for low and high heating rates, respectively. Moreover, a method for obtaining the value of E based on the non-isothermal JMA analysis was proposed. The value of E was determined as ~185 and 191 kJ/mol respectively for low and high heating rates, which are consistent with the value determined from the Kissinger plot for all heating rates.     

Characterization of mechanically alloyed ternary Fe–Ti–Al powders

The effects of Ti-substitution for Fe in the Fe₃Al system on the mechanical alloying process were investigated. For this purpose, blended elemental powders with the following nominal compositions (at.%): Fe₇₅Al₂₅, Fe₇₀Ti₅Al₂₅, Fe₆₅Ti₁₀Al₂₅, Fe₆₀Ti₁₅Al₂₅, were mechanically alloyed in a high energy attritor-type ball milling system for up to 100 h. The structural evolution in these powders was characterized by scanning electron microscopy, differential thermal analysis and X-ray diffraction techniques. It was found that elemental powders were progressively transformed into nanocrystalline solid solutions during mechanical alloying. The addition of Ti in the powders shortened the milling time for solid solution formation. With increasing Ti content, the grain size of the solid solutions decreased, but the lattice parameter increased. Upon heating, the milled powders were transformed into ordered (Fe,Ti)₃Al intermetallic compounds in an extended range of temperature (from 350 to 500°C). Ti addition enhanced the occurrence of DO₃ ordering in heated powders.     

室温应变速率及Al含量对FeAl合金拉伸性能的影响

研究了初始应变速率在１．３９×１０＾４￣６．９５×１０＾－１ｓ＾－１范围内Ｆｅ－４０Ａｌ的室温拉伸性能。结果发现，应变速率对ＦｅＡｌ合金室温下的断裂延伸率屈服强度和抗拉强度均有不同程度的影响，其中对断裂延伸率的影响最为显著。应变速率对ＦｅＡｌ合金力学性能的影响程度还与Ａｌ含量有关，Ｆｅ－３６．５Ａｌ较Ｆｅ－４０Ａｌ合金受应变速率的影响更大，研究结果还表明，Ａｌ含量还影响着ＦｅＡｌ合金拉伸断口中穿晶     

Synthesis of hydrophobic Ni-VN alloy powder by ball milling

This is the first report discussing the synthesis of hydrophobic alloy powders consisting of Ni and transition metal nitride (vanadium nitride (VN)) at different proportions through mechanical alloying. The milled alloy powder showed very good resistance to wetting when it was placed in a beaker containing water. The maximum contact angle of 150° with water was recorded for the alloy composition of Ni-75 (wt.%) VN when the powder was loosely sprayed on a glass slide. Few working examples also elucidated the hydrophobic nature of the as-prepared alloy powder. The optimised alloyed powder composition and its phase and morphology as well as the time of milling for maximum hydrophobicity were established with the help of X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) for phase and morphology analysis, respectively. The unique chemistry of toluene with elemental Ni and transition metal nitride VN as characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy led to the development of hydrophobicity in the ball milled powder.