Amorphization in the Al---C system by mechanical alloying

Mechanical alloying of a powder mixture of elemental Al and graphite has been performed in a high-energy ball mill. The structural evolution has been characterized by X-ray diffraction and transmission electron microscopy. The carbide Al₄C₃ is first formed as an intermediate product. Further milling leads to destabilization of Al₄C₃. It is proposed that destabilization of Al₄C₃ is induced by the accumulated defects and the high pressure due to collision of the balls. Balling milling of the elemental Al---C powder mixture finally results in a f.c.c. solid solution with a carbon content up to 23 at%. Whereas an amorphous phase is formed in the composition range of 28–50 at% C.     

Structure and magnetic properties of Fe-based powders prepared by mechanical alloying

FeSiAlCr alloy powders were prepared by mechanical alloying, the milling time were 20 h, 40 h, 60 h and 80~h, respectively. Powders morphology was studied by SEM. Microstructure of powders milled for various times were analyzed by XRD. The complex permittivity and complex permeability of four powders were tested in the frequency range from 0.5 to 18 GHz, and their microwave absorption properties were analyzed. It was found that the particle size of powders milled for 80~h was less than 2μm. Silicon and aluminum atoms were dissolved into the crystal lattice of iron, and chromium atoms can form alloy with iron atoms. The minimum peak value of reflectivity can reach to -11.3 dB at the frequency of 4.3 GHz for 80 h milling powders, and the other one was -6 dB at 16.5 GHz.     

Metastable Ti---Ni---Fe---Si alloys prepared by mechanical alloying

The phase formation and physical properties of mechanically alloyed Ti₅₆Ni₁₈Fe₁₀Si₁₆ have been investigated. The as-milled samples are amorphous and undergo a transition to the icosahedral quasi-crystalline phase on annealing at about 1025 K. Mechanical alloying in the presence of an additive of 1% quasi-crystalline phase yielded the same phase directly. Alloys have been studied by X-ray diffraction. Mössbauer spectroscopy and magnetic susceptibility methods. These results may be compared with those in the literature for amorphous and quasi-crystalline alloys of similar composition prepared by rapid solidification from the melt. In all cases the alloys produced by mechanical alloying show a greater concentration of open volume defects and in the icosahedral phase, a greater degree of disorder and largerphason strains. Hydrogen diffusion studies of these alloys have shown that the mean interatomic distance increases for short hydrogenation times, but that for longer hydrogenation times the hydrogen increases local atomic order which results in a reduction of mean interatomic distances.     

Reduction reaction in Al-CuO powder mixture driven by mechanical alloying

lINTR0DUCTIONNan0-sizedparticlesreinforcedmetalmatrixcomposites["'Jandnano-sizedelementalmetalparticles['~'Jcanbeobtainedbycertainreactionsduringball-millingwhicharedifficulttooccurunderconventionalconditions.ThemechanicallydrivenreductionreactionofCuO(orCu,O) M-Cu M.O.(M=Al,Ca,Mn,Ti,Fe,Ni,etc.)hasbeenappliedtoproducenan0-sizedCuparticles.However,themechanismofthedis-placementreactionprocesshasnotbeenwellun-derstood.InSchaffer'sopinion,localreactionisbelievedtooccurspontane0uslywhe…     

Spark plasma sintering consolidation of nanostructured TiC prepared by mechanical alloying

Spark plasma sintering technique was used for the consolidation of nanostructured titanium carbide synthesized by mechanical alloying in order to avoid any important grain growth of the compact materials. The TiC phase was obtained after about 2 h of mechanical alloying. Towards the end of the milling process (20 h), the nanocrystalline powders reached a critical size value of less than 5 nm. Some physical and mechanical properties of the consolidated carbide were reported as a function of the starting grain size powders obtained after different mechanical alloying durations. The crystalline grain size of the bulk samples was found to be increased to a maximum of 120 nm and 91 nm for carbides mechanically alloyed for 2 h and 20 h respectively. The Vickers hardness showed to be improved to about 2700 Hv for a maximum density of 95.1% of the bulk material.     

机械合金化法制备金锡合金

采用高能球磨机械合金化法制备了Au-20%Sn合金,分析了合金物相、组织和硬度随球磨时间的变化规律,探讨了合金塑性与合金组织及制备工艺的关系。结果表明:采用高能球磨机械合金化法可以制备Au-20%Sn合金;随球磨时间的增加,Au-20%Sn的合金化程度增加,组织中的金属间化合物逐渐增多,最终基本上为δ相和ζ′相;合金的硬度随球磨时间的延长逐渐升高,并在球磨60min后获得最高硬度104.2HV,然后开始下降;球磨后的合金粉末在190℃×2h的烧结过程中发生了不同程度的再结晶和晶粒长大,再结晶程度随球磨时间的延长而增加,导致烧结后合金硬度在球磨时间超过60min后反而下降。     

Fabrication of Ti-Cu-Ni-Al amorphous alloys by mechanical alloying and mechanical milling

Ti-based amorphous alloy powders were synthesized by the mechanical alloying (MA) of pure elements and the mechanical milling (MM) of intermetallic compounds. The amorphous alloy powders were examined by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Scanning electron micrographs revealed that the vein morphology of these alloy powders shows deformation during the milling. The energy-dispersive X-ray spectral maps confirm that each constituent is uniformly dispersed, including Fe and Cr. The XRD and DSC results showed that the milling time required for amorphization for the MA of pure elements was longer than that of the MM for intermetallic compounds. The activation energy and crystallization temperature of the MA powder are different from those of the MM powder.     

机械合金化法制备Al—Cu—Fe纳米非晶合金

采用行星式高能球磨机制备了Al80-xCuxFe20(x=20-40）三元非晶纳米合金粉末,分析了不同球磨时间及热处理工艺对粉末结构、颗粒大小等的影响。结果表明：成分为Al40Cu40Fe20的粉末球磨时逐步非晶化,球磨33h后,非晶化程度最大,最小颗粒尺寸达到5．6nm;进一步球磨,非晶晶化,颗粒尺寸增大;成分为Al80-xCuxFe20(x=20,25,30)的粉末球磨90h后,得到非晶,最小颗粒尺寸为3．4nm。球磨制备的Al-Cu-Fe非晶粉末具有铁磁性。用DSC测量了其晶化温度（Tc),Tc≈873℃。     

Phase evolution of Mg–Al–Zr nanophase alloys prepared by mechanical alloying

Al–Mg and Al–Mg–Zr alloys were processed by mechanical alloying. The phase constitution of the powders was strongly dependent on the composition of the starting mixture. In as-milled powders, an Al(Mg) solid solution was formed with up to 40 at% Al, which after annealing transformed to the equilibrium β-Al₃Mg₂ phase. For high Mg concentrations (60–90 at%) the dominant phase was γ-Al₁₂Mg₁₇ in accordance with the equilibrium phase diagram. The addition of Zr led to the appearance of Zr–Al intermetallics causing Mg to precipitate out of the Al(Mg) solution. The effect of zirconium was also to refine the structure and to retard grain growth.     

Nanophase intermetallic FeAl obtained by sintering after mechanical alloying

The preparation of bulk nanophase materials from nanocrystalline powders has been carried out by the application of sintering at high pressure. Fe–50 at.%Al system has been prepared by mechanical alloying for different milling periods from 1 to 50 h, using vials and balls of stainless steel and a ball-to-powder weight ratio (BPR) of 8:1 in a SPEX 8000 mill. Sintering of the 5 and 50 h milled powders was performed under high uniaxial pressure at 700 °C. The characterization of powders from each interval of milling was performed by X-ray diffraction, Mössbauer spectroscopy, scanning and transmission electron microscopy. After 5 h of milling formation of a nanocrystalline α-Fe(Al) solid solution that remains stable up to 50 h occurs. The grain size decreases to 7 nm after 50 h of milling. The sintering of the milled powders resulted in a nanophase-ordered FeAl alloys with a grain size of 16 nm. Grain growth during sintering was very small due to the effect of the high pressure applied.     

合金元素对单相渗碳体磁性粉体制备及性能的影响

通过机械合金化和真空退火热处理的方法制备了单相渗碳体粉末,并结合第一性原理计算,分析了Mn、Cr和Si对合金渗碳体的成相能力及渗碳体磁学性能的影响.结果表明,机械合金化+600℃真空热处理可获得单相渗碳体.Si的加入完全抑制了渗碳体的生成,而加入Mn、Cr对渗碳体生成有促进作用.Cr、Mn合金化的渗碳体的粉末饱和磁化强...     

Carbon solubility in Cu-based composite prepared by mechanical alloying

The powder mixture of Cu and graphite was mechanically alloyed （MA） in an oscillating type ball mill. The milling time was varied in order to investigate its influence on the microstructural evolution of mechanically alloyed powders. The phase constituent, alloying characteristics, grain size and lattice distortion of these powders were determined by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results show that the C is confirmed to dissolve in the Cu lattice, forming solid solution of carbon in copper the lattice parameter of copper increases with carbon concentration increasing, up to a saturation value of about 4%C（mass fraction）. Higher ball-mill energy is beneficial for twins and nanograin formation.     

Synthesis of nanocrystalline NiAl by mechanical alloying

The nanocrystalline NiAl intermetallic compound was synthesized by mechanical alloying of the elemental powders. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometery, scanning electron microscopy and microhardness measurements. The mechanical alloying resulted in the gradual formation of nanocrystalline NiAl with a grain size of 20 nm. It was found that NiAl phase develops by continuous diffusive reaction at Ni/Al layers interfaces. The NiAl compound exhibited high microhardness value of about 1035 Hv.     

X-ray diffraction study on Ni---Al---Se amorphization by mechanical alloying

In this paper, the amorphization process in mechanical alloyed Ni---Al---Se powders has been investigated by X-ray diffraction. The influence of Se on the amorphization of Ni---Al alloys, and the influence of milling time on the powder structure, microcrystallites size and phases lattice distortion are presented. Also, the Fe and Cr content from the milling medium, after 400 h, was determined.     

Multi-scaled polymer-based composite materials synthesized by mechanical alloying

Multi-scaled composite materials are of great importance, because they exhibit higher mechanical properties than those attained using conventional fillers or polymer blends. In this work, multi-scaled composite materials based on ultra-high-molecular weight polyethylene (UHMWPE), quasicrystals, polyimide and bronze are investigated for use in the moving parts of machines, gears, bearings, and sliding elements. The main object is to investigate the process of fabricating such composite materials, and to check if these materials are reproducible and reliable to an industrial extent. The specimens were prepared using a high-energy planetary mill. When milled with bronze, the quasicrystalline phase was dissolved into an intermetallic solid solution; milling with polymers showed to conserve the quasicrystalline phase, whereas the crystallization of UHMWPE was achieved during the milling process. Tribological study of consolidated samples showed an increase in the wear resistance for the bronze-containing composite materials. In comparison with pure UHMWPE, the polyimide-based specimen exhibited higher strength and hardness. This work has demonstrated the possibility of producing composite materials with acceptable and reliable properties using the mechanical alloying technology.     

添加W对机械合金化TiAl合金显微组织和性能的影响

采用机械合金化结合粉末冶金技术制备了Ti-44．7A1-xW（at％）合金材料。采用透射电镜、扫描电镜和金相显微镜研究不同W添加量对机械合金化TiAl基合金的显微组织和高温抗氧化性能的影响，并对合金的力学性能进行测试。研究表明，通过机械合金化在TiAl基合金系统中添加微量W元素会形成新的固溶体相，这种新成分相大大提高TiAl基合金的抗弯强度σb当W添加量为1．0at％时，σb达到峰值；随后随着W含量的增加，抗弯强度降低。W元素的添加有效的制约了合金基体的内部氧化，使TiAl合金的高温抗氧化性能明显提高。     

机械合金化过程中Fe50Als50二元系的结构演变

利用高能球磨和后续热处理技术制备纳米晶Fe5A150（摩尔分数，％）合金粉体。采用X射线衍射、透射电镜和扫描电镜对元素混合粉在机械合金化过程中的结构演变及热处理对合金化粉体结构的影响等进行分析，讨论其机械合金化合成机制。结果表明：球磨过程中Al向Fe中扩散，形成Fe（A1）固溶体。机械合金化合成Fe（Al）遵循连续扩散混合机制；球磨30h后，粉体主要由纳米晶Fe（A1）构成，晶粒尺寸5．65nm；热处理导致Fe（A1）纳米晶粉体有序度提高，转变为有序的B2型FeAl金属间化合物，粉体的晶粒尺寸增大，但仍在纳米尺度范围。     

Preparation of nanocomposite alumina–Sn2Fe by mechanical alloying

Nanocomposites of Al₂O₃ and Sn₂Fe were prepared by ball milling alumina with elemental Sn and Fe. Samples were prepared with molar ratios of Al₂O₃ and Sn₂Fe of 1:1 and 2:1. Materials produced in this way have been characterized by X-ray diffraction techniques as well as ⁵⁷Fe Mössbauer effect spectroscopy as a function of milling time. The nanosized grains show a distribution of particle sizes along with some residual elemental components. Preliminary investigations of electrochemical cells indicate that these materials show promise as possible electrodes for Li-ion cells.     

Characterization and formation mechanism of nanocrystalline (Fe,Ti)3Al intermetallic compound prepared by mechanical alloying

The nanocrystalline (Fe,Ti)₃Al intermetallic compound was synthesized by mechanical alloying (MA) of elemental powder with composition Fe₅₀Al₂₅Ti₂₅. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry and microhardness measurements. Morphology and cross-sectional microstructure of powder particles were characterized by scanning electron microscopy. It was found that a Fe/Al/Ti layered structure was formed at the early stages of milling followed by the formation of Fe(Ti,Al) solid solution. This structure transformed to (Fe,Ti)₃Al intermetallic compound at longer milling times. Upon heat treatment of (Fe,Ti)₃Al phase the degree of DO₃ ordering was increased. The (Fe,Ti)₃Al compound exhibited high microhardness value of about 1050 Hv.