Microstructural Evolution during Mechanical Alloying and Hot Pressing of a Powder Blend of Aluminium and 316 Stainless Steel

2006 ◽  
Vol 114 ◽  
pp. 211-218
Author(s):  
A. Samanta ◽  
P.P. Chattopadhyay ◽  
Witold Łojkowski ◽  
Stanislaw Gierlotka ◽  
Hans Jorg Fecht ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Property ◽  
Stainless Steel ◽  
Hot Pressing ◽  
Milled Powder ◽  
Phase Evolution ◽  
Xrd Analysis ◽  
High Energy ◽  
Nanocrystalline Powders ◽  
Powder Blend

The paper examines the phase evolution in blends consisting of different proportions of stainless steel (SS316) and Al (0, 25, 65 and 85 wt. %) powders during high-energy ball milling by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy. An attempt has also been made to study the mechanical property of the bulk samples obtained by hot pressing the ball milled powder blend at suitable a temperature and pressure. The results of microstructural changes and mechanical property and the ability of consolidation of the amorphous/nanocrystalline powders by high-pressure techniques to develop engineering components has been discussed and highlighted.

High Strength Bulk Nanostructured 2219 Al Alloy Produced by High Energy Ball Milling and Hot Pressing

2008 ◽  
Vol 584-586 ◽  
pp. 97-101 ◽  
Author(s):  
T. Shanmugasundaram ◽  
V. Subramanya Sarma ◽  
B.S. Murty ◽  
Martin Heilmaier
Keyword(s):  
Mechanical Properties ◽  
Ball Milling ◽  
Hot Pressing ◽  
Xrd Analysis ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Coarse Grained ◽  
Nanocrystalline Powders ◽  
Al Alloy ◽  
Energy Ball

The microstructure and mechanical properties of nano-crystalline 2219 Al alloy (Al-6.4Cu-0.29Mn, all in wt %) was studied. Nanocrystalline powders were produced from gas atomized 2219 Al alloy powders by high energy ball milling at room temperature. Powders were collected at different milling times and X-ray diffraction (XRD) analysis was used to evaluate grain size. High Vickers hardness (250HV), high compressive strength (920 MPa) and low ductility (2%) were observed in unimodal bulk nanostructured 2219 Al alloys consolidated to 99% density by hot pressing (HP). In addition, these nanocrystalline powders were blended with 15, 30 and 50% of (gas atomized) coarse-grained powders to obtain balanced mechanical properties of enhanced yield and ultimate strength and reasonable ductility and toughness as compared to either conventional or nanocrystalline 2219 alloys.

Microstructure and superconducting properties of attrition-milled Bi2Sr2CaCu2Ox

1994 ◽  
Vol 9 (2) ◽  
pp. 297-304 ◽  
Author(s):  
J.S. Luo ◽  
H.G. Lee ◽  
S.N. Sinha
Keyword(s):  
Electron Microscopy ◽  
Milled Powder ◽  
High Energy ◽  
Double Layers ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Steel Tank ◽  
Practical Implications

The microstructure and superconducting properties of Bi2Sr2CaCu2Ox (Bi-2212) during high-energy attrition milling were investigated in detail by a combination of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and magnetization techniques. The starting superconducting powder was milled in a standard laboratory attritor using yttria-stabilized ZrO2 balls and a stainless steel tank. After selected time increments, the milling was interrupted and a small quantity of milled powder was removed for further analysis. It was found that the deformation process rapidly refines Bi-2212 into nanometer-size crystallites, increases atomic-level strains, and changes the plate-like morphology of Bi-2212 to granular submicron clusters. At short milling times, the deformation seems localized at weakly linked Bi-O double layers, leading to twist/cleavage fractures along the {001} planes. The Bi-2212 phase decomposes into several bismuth-based oxides and an amorphous phase after excessive deformation. The superconducting transition is depressed by about 10 K in the early stages of milling and completely vanishes upon prolonged deformation. A deformation mechanism is proposed and correlated with the evolution of superconducting properties. The practical implications of these results are presented and discussed.

AN INVESTIGATION INTO MECHANOCHEMICAL SYNTHESIS OF NANOCRYSTALLINE HEXAFERRITE POWDER

2011 ◽  
Vol 25 (07) ◽  
pp. 987-993
Author(s):  
S. SADEGHI-NIARAKI ◽  
S. A. SEYYED EBRAHIMI ◽  
SH. RAYGAN
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Milled Powder ◽  
Particle Morphology ◽  
Average Crystallite Size ◽  
Phase Evolution ◽  
High Energy ◽  
Strontium Hexaferrite ◽  
Electron Microscopes

Nanocrystalline strontium hexaferrite powder has been prepared by a new mechanochemical method in which the single phase hexaferrite was obtained via a sol–gel autocombustion process followed by an intermediate high energy milling step and subsequent annealing. The effects of the intermediate milling on the phase evolution, crystallite size and annealing behavior of the final products were investigated using the X-ray diffraction (XRD) technique. The single phase strontium hexaferrite was obtained at an annealing temperature of 800°C, while this temperature was 1,000°C for the powder synthesized without milling. It could be seen that an intermediate milling accelerates the formation of strontium hexaferrite during the calcination process. The results showed that in the milled powder, the average crystallite size of the ferrite was about 40 nm and much smaller than that of the nonmilled powder. Magnetic properties were also measured by a vibrating sample magnetometer (VSM). The particle morphology was then studied by scanning and transmission electron microscopes (SEM and TEM).

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

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.

scholarly journals Effect of Mechanical Milling and Cold Pressing on Co Powder

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
A. S. Bolokang ◽  
M. J. Phasha ◽  
D. E. Motaung ◽  
S. Bhero
Keyword(s):  
Compaction Pressure ◽  
Milled Powder ◽  
Xrd Analysis ◽  
High Energy ◽  
Lattice Parameter ◽  
Exothermic Peak ◽  
Cold Pressing ◽  
First Order Phase Transition ◽  
Fcc Phase ◽  
First Time

Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at 615C°. Upon annealing at 700C°, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at 615C° corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with a=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters a=b=3.80 and c=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter a shrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at 750C°, the FCT to FCC transition occurred, yielding the FCC phase with a=3.51 Å.

scholarly journals Effects of milling temperature and time on phase evolution of Ti-based alloy

2021 ◽  
pp. 55-55
Author(s):  
F. Kristaly ◽  
M. Sveda ◽  
A. Sycheva ◽  
T. Miko ◽  
A. Racz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Milling Time ◽  
Nanocrystalline Structure ◽  
Phase Evolution ◽  
High Energy ◽  
Particle Size Analysis ◽  
Size Analysis ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Milling Temperature

Ti50Cu25Ni20Sn5 (at.%) powder was subjected to high-energy ball milling at room temperature and -78?C. As a function of the milling time, evaluation of phases, morphology and the refinement of grain size were investigated by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and laser-diffraction particle size analysis (PSA). The transformation of the crystalline structure into an amorphous structure and then the transformation into a nanocrystalline structure during further milling was detected. The stress-induced martensitic transformation has taken place after 30 min milling time at both temperatures, the cubic Cu(Ni,Cu)Ti2 phase transforms into the orthogonal structure. The hardness value of powders after 150 min milling time increases from 506 to 780 HV0.01. The milling temperature does not significantly influence the amount of amorphous fraction (33-36 wt.%) but the composition of amorphous content is more influenced by temperature. The interval of crystallite size was between 1.2 and 11.7 nm after 180 min of milling. The amount and the cell parameters of the Sn-containing phases are different between the two milling experiments, owing to the diffusion coefficients of the Sn atom differ to a large extent.

scholarly journals Microstructural and Magnetic Behavior of Nanocrystalline Fe-12Ni-16B-2Si Alloy Synthesis and Characterization

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1679
Author(s):  
Kaouther Zaara ◽  
Mohamed Khitouni ◽  
Lluisa Escoda ◽  
Joan Saurina ◽  
Joan-Josep Suñol ◽  
...  
Keyword(s):  
Solid Solution ◽  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Milling Time ◽  
Milled Powder ◽  
Magnetic Behavior ◽  
Phase Evolution ◽  
High Energy ◽  
Refined Microstructure ◽  
Hard Magnetic Properties

The nanocrystalline Fe70Ni12B16Si2 (at.%) alloy was prepared by mechanical alloying (MA) of elemental powders in a high-energy planetary ball mill. Phase evolution, microstructure, thermal behavior and magnetic properties were investigated. It was found that a body-centered cubic structured solid solution started to form after 25 h milling and a faced-centered cubic structure solid solution started to form after 50 h of milling; its amount increased gradually with increasing milling time. The BCC and the FCC phases coexisted after 150 h of milling, with a refined microstructure of 13 nm and a 10 nm crystallite size. The as-milled powder was annealed at 450 °C and 650 °C and then investigated by vibrating sample magnetometry (VSM). It was shown that the semi-hard magnetic properties are affected by the phase transformation on annealing. The saturation magnetization decreases after annealing at 450 °C, whereas annealing at 650 °C improves the magnetic properties of 150 h milled powders through the reduction of coercivity from 109 Oe to 70 Oe and the increase in saturation magnetization.

scholarly journals TDS Measurement of Hydrogen Released from Stainless Steel Oxidized in H2O-Containing Atmospheres

2006 ◽  
Vol 522-523 ◽  
pp. 163-170 ◽  
Author(s):  
Akira Yamauchi ◽  
Yuji Yamauchi ◽  
Yuko Hirohata ◽  
Tomoaki Hino ◽  
Kazuya Kurokawa
Keyword(s):  
Electron Microscopy ◽  
Mechanical Property ◽  
Stainless Steel ◽  
Thermal Desorption Spectroscopy ◽  
Scale Morphology ◽  
Cr2o3 Scale ◽  
Glow Discharge Spectroscopy ◽  
Dissolved Hydrogen ◽  
Scanning Electron ◽  
Main Factor

Hydrogen dissolved in the Cr2O3 scale formed on the stainless steel in the H2O-containing atmospheres is observed by TDS (thermal desorption spectroscopy) measurements. The amount of dissolved hydrogen in the Cr2O3 scale reaches a maximum about 0.32 mol% when the H2O concentration in the gas reaches 20%. It was found from GDS (glow discharge spectroscopy) measurements that hydrogen may exist at the oxide scale / substrate interface or in Cr2O3 scale bounded that interface. However, results from the Vickers hardness and the observation of scale morphology by SEM (scanning electron microscopy), hydrogen dissolved in the Cr2O3 scale would have little effect on a decrease in the mechanical property of the Cr2O3 scale. Therefore, hydrogen dissolved in the Cr2O3 scale may not be main factor of the deterioration of the Cr2O3 scale.

Synthesis of Nickel/Ba-Hexaferrite Magnetic Nano-Composite via Mechanical Alloying Route

2013 ◽  
Vol 829 ◽  
pp. 520-524
Author(s):  
Issa Sobhani ◽  
Abolghasem Ataie ◽  
Mahdiye Ijavi ◽  
Zoya Sadighi
Keyword(s):  
Magnetic Properties ◽  
Milling Time ◽  
Phase Evolution ◽  
Xrd Analysis ◽  
High Energy ◽  
Argon Atmosphere ◽  
Metallic Nickel ◽  
Process Conditions ◽  
Nano Composite ◽  
20 Nm

In this study, nickel and Ba-hexaferrite powders were subjected to high energy mechanical milling in argon atmosphere to produce nickel/Ba-hexaferrite magnetic nanocomposite. Effects of milling time and Ni amount on the phase evolution, morphology and magnetic properties of the products have been investigated by XRD, FESEM/SEM and VSM, respectively. XRD analysis of nanocomposite indicated only Ni peaks after 5 h milling which implied the embedding of Ba-hexaferrite particles inside the metallic nickel. FESEM results revealed that the increasing of the milling time up to 30 h reduced nanocomposite particles size into 20 nm. VSM results showed that the magnetic properties of the nickel/Ba-hexaferrite nanocomposite were affected by the process conditions. The highest saturation magnetization (33.8emu/g) was obtained for the sample containing 30 wt% Ni milled for 20 h Ni series of powder mixture. In addition, it was found that by increasing the milling time coercive field decreases.

The structural transformation of anatase TiO2 by high-energy vibrational ball milling

1999 ◽  
Vol 14 (3) ◽  
pp. 841-848 ◽  
Author(s):  
Suchitra Sen ◽  
M. L. Ram ◽  
S. Roy ◽  
B. K. Sarkar
Keyword(s):  
Electron Microscopy ◽  
Ball Milling ◽  
Structural Transformation ◽  
Milled Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
First Time ◽  
Pressure Phase

The structural transformation of anatase TiO2 by high-energy vibrational ball milling was studied in detail by different analytical methods of x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This structural transformation involves both phase transition and nanoparticle formation, and no amorphization was observed. The crystallite size was found to decrease with milling time down to nanometer size ∼13 nm and approaching saturation, accompanied by phase transformation to metastable phases, i.e., TiO2(II), which is a high-pressure phase and TiO2(B), which was identified in ball-milled powder reported for the first time in this paper. These phases eventually started transforming to rutile by further milling.

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