Effect of Hydrogen on Formation of Fe-Al Nanoparticles by Mechanical Milling

Nanocrystalline powders of iron aluminum alloy of the Fe82Al18 nominal composition were prepared under air, hydrogen and nitrogen atmospheres from the Fe and Al elemental powders by mechanical alloying and also from the conventionally cast Fe82Al18 alloy by the high-energy ball milling. The intensive plastic deformation during high-energy mechanical treatment has introduced high concentrations of open volume defects and contributed to a rapid decrease in the crystallite size down to a nanoscopic range.The hydrogen atmosphere was found to be the most efficient for the Fe-Al mechanical alloying since it has resulted into the fully alloyed Fe82Al18 after 30 h of milling. On the other hand, the nitrogen and air atmosphere have slightly prevented mechanical alloying and after the same milling time the pure iron particles were still detected in the powder mixtures. This partial suppression of the mechanical alloying process is explained by a formation of thin iron nitride and/or oxide layers on the surface of Fe particles preventing mutual inter-diffusion of Fe and Al atoms.

Download Full-text

Effect of Milling Parameters on the Development of a Nanostructured FCC–TiNb15Mn Alloy via High-Energy Ball Milling

Metals ◽

10.3390/met11081225 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1225

Author(s):

Cristina García-Garrido ◽

Ranier Sepúlveda Sepúlveda Ferrer ◽

Christopher Salvo ◽

Lucía García-Domínguez ◽

Luis Pérez-Pozo ◽

...

Keyword(s):

Mechanical Alloying ◽

Ball Mill ◽

Milling Time ◽

High Energy ◽

Planetary Mill ◽

Nominal Composition ◽

Mechanically Alloyed ◽

Milling Parameters ◽

Energy Ball ◽

Full Conversion

In this work, a blend of Ti, Nb, and Mn powders, with a nominal composition of 15 wt.% of Mn, and balanced Ti and Nb wt.%, was selected to be mechanically alloyed by the following two alternative high-energy milling devices: a vibratory 8000D mixer/mill® and a PM400 Retsch® planetary ball mill. Two ball-to-powder ratio (BPR) conditions (10:1 and 20:1) were applied, to study the evolution of the synthesized phases under each of the two mechanical alloying conditions. The main findings observed include the following: (1) the sequence conversion evolved from raw elements to a transitory bcc-TiNbMn alloy, and subsequently to an fcc-TiNb15Mn alloy, independent of the milling conditions; (2) the total full conversion to the fcc-TiNb15Mn alloy was only reached by the planetary mill at a minimum of 12 h of milling time, for either of the BPR employed; (3) the planetary mill produced a non-negligible Fe contamination from the milling media, when the highest BPR and milling time were applied; and (4) the final fcc-TiNb15Mn alloy synthesized presents a nanocrystalline nature and a partial degree of amorphization.

Download Full-text

Effect of Milling Speed on the Synthesis of In-Situ Cu-25 Vol. % WC Nanocomposite by Mechanical Alloying

Jurnal Teknologi ◽

10.11113/jt.v59.2599 ◽

2012 ◽

Vol 59 (2) ◽

Author(s):

Nurulhuda Bashirom ◽

Nurzatil Ismah Mohd Arif

Keyword(s):

Stainless Steel ◽

Mechanical Alloying ◽

Weight Ratio ◽

High Energy ◽

Milling Process ◽

Nominal Composition ◽

X Ray Diffraction ◽

The Matrix ◽

Steel Balls

This paper presents a study on the effect of milling speed on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to composition Cu-34.90 wt% W-2.28 wt% C. The powders were milled in different milling speed; 400 rpm, 500 rpm, and 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result showed the formation of W2C phase after milling for 400 rpm and as the speed increased, the peak was broadened. No WC phase was detected after milling. Increasing the milling speed resulted in smaller crystallite size of Cu and proven to be in nanosized. Based on SEM result, higher milling speed leads to the refinement of hard W particles in the Cu matrix. Up to the 600 rpm, the unreacted W particles still existed in the matrix showing 20 hours milling time was not sufficient to completely dissolve the W.

Download Full-text

Obtaining of the Ir-Al Nanocrystalline Powders by Mechanical Alloying

Materials Science Forum ◽

10.4028/www.scientific.net/msf.672.171 ◽

2011 ◽

Vol 672 ◽

pp. 171-174

Author(s):

Ionel Chicinaş ◽

P. Cârlan ◽

Florin Popa ◽

Virgiliu Călin Prică ◽

Lidia Adriana Sorcoi

Keyword(s):

Mechanical Alloying ◽

Particle Morphology ◽

High Energy ◽

Atomic Ratio ◽

Planetary Mill ◽

Nanocrystalline Powders ◽

Alloy Formation ◽

X Ray Diffraction ◽

Chemical Homogeneity ◽

Diffraction Patterns

The Ir-Al powder in the 1:1 atomic ratio was obtained by high energy mechanical alloying in a Pulverisette 4 Fritch planetary mill. The final product was obtained after 28 h of milling in argon atmosphere. Alloy formation was investigated by X-ray diffraction. After 4 h of milling the new structure of IrAl compound is found in the diffraction patterns. The obtained powders are nanocrystalline with a mean crystallite size of 11 nm after 28 h of milling. The particle morphology and the chemical homogeneity were studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX). It was found that the obtained compound present large particles composed by smaller one.

Download Full-text

Nanocomposite Bi(Sb)Te(Se) Materials by Cryogenic Mechanical Alloying and Optimized High Pressure Hot-pressing

MRS Proceedings ◽

10.1557/opl.2012.1369 ◽

2012 ◽

Vol 1456 ◽

Author(s):

Tsung-ta E. Chan ◽

Rama Venkatasubramanian ◽

James M. LeBeau ◽

Peter Thomas ◽

Judy Stuart ◽

...

Keyword(s):

Mechanical Alloying ◽

Hot Pressing ◽

High Energy ◽

Structural Features ◽

Milling Process ◽

Nanocrystalline Powders ◽

Full Density ◽

Seebeck Coefficients ◽

The Matrix ◽

Cryogenic Process

ABSTRACTNanocomposite Bi2Te3 based alloys are attractive for their potentially high thermoelectric figure-of-merit (ZT) around room temperature. The nano-scale structural features embedded in the matrix provide more scattering of phonons and can thus reduce the lattice thermal conductivity. To further take advantage of such nanocomposite structures, we focus on the development of nanocrystalline Bi(Sb)Te(Se) powders by high energy cryogenic mechanical alloying followed by an optimized hot pressing process. This approach is shown to successfully produce Bi(Sb)Te(Se) alloy powders with grain size averaging about 9 nm for n-type BiTe(Se) and about 16 nm for p-type Bi(Sb)Te respectively. This cryogenic process offers much less milling time and prevents thermally activated contamination or imperfections from being introduced during the milling process. The nanocrystalline powders are then compacted at optimized pressures and temperatures to achieve full density compactions and preserve the grain sizes effectively. The resulting nano-bulk materials have optimal Seebeck coefficients and are expected to have improved ZT. Thermoelectric properties and microstructure studies by X-ray diffraction and transmission electron microscopy will also be presented and discussed.

Download Full-text

Enhanced Thermoelectric Figure-of-merit at Room Temperature in Bulk Bi(Sb)Te(Se) With Grain Size of ∼100nm

MRS Proceedings ◽

10.1557/opl.2013.948 ◽

2013 ◽

Vol 1543 ◽

pp. 93-98 ◽

Cited By ~ 1

Author(s):

Tsung-ta E. Chan ◽

Rama Venkatasubramanian ◽

James M. LeBeau ◽

Peter Thomas ◽

Judy Stuart ◽

...

Keyword(s):

Grain Size ◽

Mechanical Alloying ◽

Grain Boundaries ◽

Figure Of Merit ◽

Room Temperature ◽

High Energy ◽

High Density ◽

Nanocrystalline Powders ◽

Bulk Materials ◽

P Type

ABSTRACTGrain boundaries are known to be able to impede phonon transport in the material. In the thermoelectric application, this phenomenon could help improve the figure-of-merit (ZT) and enhance the thermal to electrical conversion. Bi2Te3 based alloys are renowned for their high ZT around room temperature but still need improvements, in both n- and p-type materials, for the resulting power generation devices to be more competitive. To implement high density of grain boundaries into the bulk materials, a bottom-up approach is employed in this work: consolidations of nanocrystalline powders into bulk disks. Nanocrystalline powders are developed by high energy cryogenic mechanical alloying that produces Bi(Sb)Te(Se) alloy powders with grain size in the range of 7 to 14 nm, which is about 25% finer compared to room temperature mechanical alloying. High density of grain boundaries are preserved from the powders to the bulk materials through optimized high pressure hot pressing. The consolidated bulk materials have been characterized by X-ray diffraction and transmission electron microscope for their composition and microstructure. They mainly consist of grains in the scale of 100 nm with some distributions of finer grains in both types of materials. Preliminary transport property measurements show that the thermal conductivity is significantly reduced at and around room temperature: about 0.65 W/m-K for the n-type BiTe(Se) and 0.85 W/m-K for the p-type Bi(Sb)Te, which are attributed to increased phonon scattering provided by the nanostructure and therefore enhanced ZT about 1.35 for the n-type and 1.21 for the p-type are observed. Detailed transport properties, such as the electrical resistivity, Seebeck coefficient and power factor as well as the resulting ZT as a function of temperature will be described.

Download Full-text

Effect of Milling Time on the Synthesis of In-situ Cu-25 Vol. % WC Nanocomposite by Mechanical Alloying

Jurnal Teknologi ◽

10.11113/jt.v59.2581 ◽

2012 ◽

Vol 59 (2) ◽

Author(s):

Nurulhuda Bashirom ◽

Hazni Fazliana Kassim

Keyword(s):

Stainless Steel ◽

Mechanical Alloying ◽

Milling Time ◽

Weight Ratio ◽

Copper Matrix ◽

High Energy ◽

Milling Process ◽

Nominal Composition ◽

Peak Broadening

This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with a nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to the composition Cu-34.90 wt.% W-2.28 wt.% C. The powders were milled in the different milling times; 16 hours, 32 hours, and 48 hours at rotational speed of 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result indicated the formation of WC after milling for 32 hours, and the peak broadening was observed at higher milling time. From SEM observations, the particle size of Cu-25 vol.% WC composites was gradually refined with increasing milling time until the homogenous microstructure was obtained at 48 hours of milling, even though there were still some unreacted W particles existed in the matrix. Increasing milling time resulted in smaller crystallite size and higher lattice strain of Cu. The overall result demonstrates that the longer milling time can be used to achieve WC reinforced copper matrix nanocomposite.

Download Full-text

Study of the Viability to Obtain Quasicrystal in the Composition AlCuFe Using High-Energy Milling, Followed by Pressing and Sintering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.660-661.426 ◽

2010 ◽

Vol 660-661 ◽

pp. 426-431

Author(s):

Rodrigo Estevam Coelho ◽

Ramon Mateus Santos Cruz ◽

Paulo Jesus Costa Esteves ◽

Silvana Garcia Viana ◽

Severino Jackson Guedes de Lima

Keyword(s):

Heat Treatment ◽

Mechanical Alloying ◽

Optical Microscopy ◽

Room Temperature ◽

Fixed Time ◽

High Energy ◽

Future Research ◽

Nominal Composition ◽

X Ray ◽

Setting Parameters

This work was observed the phase formations of the mixture Al-Cu-Fe processed vial mechanical alloying, powders pressing at room temperature and subsequent heat treatment. The mixture of powders was made on the nominal composition Al65Cu20Fe15. A mill of high energy of the horizontal atrittor type was used to process the powders mixtures, in fixed time of two hours of milling. After milling, the powders were pressing in a die closed, with a diameter of about 28mm. The samples were observed by optical microscopy and analyzed X-ray diffractometry. The results obtained in this study provide a basis for setting parameters may be used as a basis for future research and possible applications.

Download Full-text

Similarities and Differences in the Microstructure of Attritor-milled Fe–Al–N Compositions

Journal of Materials Research ◽

10.1557/jmr.1997.0135 ◽

1997 ◽

Vol 12 (4) ◽

pp. 947-952

Author(s):

J. C. Rawers ◽

D. Cook

Keyword(s):

Grain Boundaries ◽

Aluminum Powder ◽

High Energy ◽

Iron Nitride ◽

Mechanical Processing ◽

Nitride Powder ◽

Metal Powders ◽

Iron Aluminum ◽

Powder Blends ◽

Micrometer Size

Although numerous studies of high-energy, ball-milled metal powders have been conducted, to date few studies have characterized the mechanical processing of identical elemental compositions of prealloyed powders and of powder blends. This study reports on the mechanical processing (attritor ball milling) in argon and nitrogen gas environments of (a) iron powder and prealloyed iron–2 wt.% aluminum powder, and (b) iron-aluminum, iron-aluminum nitride, and iron-iron nitride powder blends. When nitrogen was milled into iron particles either from nitride powder or by gas infusion, the nitrogen dissolved interstitially in bcc-Fe (principally at the grain boundaries) or was present as bct-Fe nanoparticles at the bcc-Fe nanograin boundaries. The resulting nitrogen distribution was independent of how the nitrogen was added. Milled blends of iron and aluminum powder and prealloyed iron-aluminum powder resulted in similar microstructures: micrometer size particles with similar nanograin size. The aluminum in the blended powder mixture developed an ultrafine distribution on the grain boundaries, but it did not become uniformly distributed within the bcc-Fe grains. In contrast, the aluminum in prealloyed Fe–Al powder remained in solid solution during the mechanical milling

Download Full-text

Influence of V and Heat Treatment on Characteristics of WMoNbTaV Refractory High-Entropy Alloy Coatings by Mechanical Alloying

Coatings ◽

10.3390/coatings11030265 ◽

2021 ◽

Vol 11 (3) ◽

pp. 265

Author(s):

Chun-Liang Chen ◽

Sutrisna

Keyword(s):

Heat Treatment ◽

Mechanical Alloying ◽

Annealing Treatment ◽

High Energy ◽

304 Stainless Steel ◽

Homogeneous Distribution ◽

High Entropy Alloy ◽

Solid Solution Phase ◽

High Entropy ◽

Steel Substrates

Refractory high-entropy alloy (RHEA) is one of the most promising materials for use in high-temperature structural materials. In this study, the WMoNbTaV coatings on 304 stainless steel substrates has been prepared by mechanical alloying (MA). Effects of V addition and subsequent heat treatment on properties of the WMoNbTaV coatings were investigated. The results show that the RHEA coatings with nanocrystalline body-centered cubic (BCC) solid-solution phase were generated by the mechanical alloying process. The presence of the V element promotes a uniform microstructure and homogeneous distribution of composition in the RHEA coatings due to improving alloying efficiency, resulting in an increase of hardness. After the annealing treatment of the RHEA coatings, microstructure homogeneity was further enhanced; however, the high affinity of Ta for oxygen causes the formation of Ta-rich oxides. Annealing also removes strain hardening generated by high-energy ball milling and thus decreases the hardness of the RHEA coating and alters microstructure evolution and mechanical properties.

Download Full-text