ROLE OF PROCESS CONTROL AGENT ON MECHANICAL ALLOYING OF NANO STRUCTURED TiAl-BASED ALLOY

2008 ◽  
Vol 22 (18n19) ◽  
pp. 2933-2938 ◽  
Author(s):  
H. BAHMANPOUR ◽  
S. HESHMATI-MANESH
Keyword(s):  
Process Control ◽  
Stearic Acid ◽  
Milled Powder ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Process Control Agent ◽  
Crystallite Sizes ◽  
Energy Ball ◽  
Milled Powders

High energy ball milling was performed on a mixture of titanium and aluminum elemental powders with a composition of Ti -48(at.%) Al . Stearic acid was added to this powder mixture as a process control agent (PCA) to study its effect on the microstructure evolution and crystallite size of the milled powder after various milling times. Phase compositions and morphology of the milled powders were evaluated using X-ray diffraction and scanning electron microscopy. Crystallite sizes of milled powders were determined by Cauchy-Gaussian approach using XRD profiles. It was shown that addition of 1wt.% of stearic acid not only minimizes the adhesion of milling product to the vial and balls, but also reduces its crystallite sizes. It has also a marked effect on the morphology of the final product.

An Investigation of the use of Stearic Acid as a Process Control Agent in High Energy Ball Milling of Nb-Al and Ni-Al Powder Mixtures

2003 ◽  
Vol 416-418 ◽  
pp. 144-149 ◽  
Author(s):  
Cláudio José da Rocha ◽  
Ricardo Mendes Leal Neto ◽  
Valéria S. Gonçalves ◽  
L.L. Carvalho ◽  
Francisco Ambrozio Filho
Keyword(s):  
Process Control ◽  
Stearic Acid ◽  
Ball Milling ◽  
High Energy ◽  
Control Agent ◽  
High Energy Ball Milling ◽  
Process Control Agent ◽  
Powder Mixtures ◽  
Energy Ball ◽  
Al Powder

Densification of Mechanically Alloyed Al5083-5wt% Y2O3 Nano Composite by Equal Channel Angular Pressing

2014 ◽  
Vol 592-594 ◽  
pp. 963-967
Author(s):  
Pravir Polly ◽  
K. Chandra Sekhar ◽  
Balasubramanian Ravisankar ◽  
S. Kumaran
Keyword(s):  
Equal Channel Angular Pressing ◽  
Single Phase ◽  
Milled Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Nano Composite ◽  
Angular Pressing ◽  
Energy Ball ◽  
Milled Powders

In the present work, Al-5083-5wt% nanoyttria powders were milled for 10, 20, 30 and 35 hrs in a high energy ball milling under optimised process parameters. The milled powders were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Milled powders exhibit nanocrystalline single phase after 10hrs of milling. Consolidation of 35 hrs milled powder was done by equal channel angular pressing (ECAP) through 90odie channel angle using route A upto three passes with and without back pressure and sintered under controlled environment. Density of ECAPed samples was measured using Archimedes principle. The density is 96% for the sample consolidated with backpressure after two passes after sintering.

Mechanical Activation of Nb75Al Powder Mixtures with Different Process Control Agents

2008 ◽  
Vol 591-593 ◽  
pp. 160-167 ◽  
Author(s):  
Valéria S. Gonçalves ◽  
Cláudio José da Rocha ◽  
Ricardo Mendes Leal Neto
Keyword(s):  
Process Control ◽  
Stearic Acid ◽  
Mechanical Activation ◽  
Milled Powder ◽  
Aggregate Size ◽  
High Energy ◽  
Powder Mixtures ◽  
Powder Charge ◽  
Energy Ball ◽  
Constant Heating

The behavior of different process control agents (PCAs) during mechanical activation of Nb75Al powder mixtures was investigated. Mechanical activation by high-energy ball milling was carried out on a shaker mill (SPEX®8000) for 1 hour. Each PCA (Stearic acid, ethanol and methanol) was added to the powder charge in two proportions (1 and 2 wt%). Shape and microstructure of activated powders (aggregates) were analyzed by scanning electron microscopy. Milled powder mixtures were uniaxially pressed in cylindrical compacts that were further vacuum reacted at a constant heating rate (30°C/min) in order to produce NbAl3 intermetallic compound. The temperature of the samples was monitored by an S-type thermocouple. The results show that the shape and the microstructure of the milled powders were strongly affected by the type and quantity of PCAs, therefore changing the reaction behavior and the densification of the produced pellets. Although ethanol was more effective to control aggregate size, best densification results were attained with 2 wt% of stearic acid.

Effect of AlCl3 Addition in Processing of TiAl-Al2O3 Nano-Composite via Mechanical Alloying

2011 ◽  
Vol 264-265 ◽  
pp. 626-630 ◽  
Author(s):  
S. Alamolhoda ◽  
Saeed Heshmati-Manesh ◽  
Abolghasem Ataie ◽  
A. Badiei
Keyword(s):  
High Energy ◽  
Control Agent ◽  
Cold Welding ◽  
Tio2 Powder ◽  
Process Control Agent ◽  
Nano Composite ◽  
Fine Grained ◽  
Al2o3 Composite ◽  
Crystallite Sizes ◽  
Energy Ball

In this paper, effect of AlCl3 addition as process control agent (PCA) during high energy ball milling of Al and TiO2 powder mixture was studied. This mechanical activation is aimed at to synthesize an ultra fine grained TiAl/Al2O3 composite. Experimental results show that AlCl3 significantly prevents severe cold welding of Al particles to milling media. Sublimation of this compound by local temperature increase due to balls collisions seems to be the main reason in prevention of severe cold welding. Samples were characterized by XRD, SEM and DTA. Mean crystallite sizes in particles of this sample and those milled with no PCA and milled with stearic acid were calculated and the results showed that smaller crystallite size is obtained in presence of AlCl3. However, DTA results revealed that addition of AlCl3, shifts aluminothermic reduction of TiO2 by Al to higher temperatures and therefore, final composite phases form at higher temperatures. Phase evolutions during further heat treatment of the powder sample milled with AlCl3 were also thoroughly studied.

SYNTHESIS OF NANO-CRYSTALLINE Cu-Cr ALLOY BY MECHANICAL ALLOYING

2012 ◽  
Vol 05 ◽  
pp. 496-501 ◽  
Author(s):  
S. SHEIBANI ◽  
S. HESHMATI-MANESH ◽  
A. ATAIE
Keyword(s):  
Mechanical Alloying ◽  
Structural Evolution ◽  
High Energy ◽  
Lattice Parameter ◽  
Control Agent ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Nano Crystalline ◽  
High Energy Ball Mill ◽  
Energy Ball

In this paper, the influence of toluene as the process control agent (PCA) and pre-milling on the extension of solid solubility of 7 wt.% Cr in Cu by mechanical alloying in a high energy ball mill was investigated. The structural evolution and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The solid solution formation at different conditions was analyzed by copper lattice parameter change during the milling process. It was found that both the presence of PCA and pre-milling of Cr powder lead to faster dissolution of Cr . The mean crystallite size was also calculated and showed to be about 10 nm after 80 hours of milling.

Combustion Synthesis of Mechanically-Activated Nb-Al Mixtures

2005 ◽  
Vol 498-499 ◽  
pp. 152-157 ◽  
Author(s):  
Fabiana Buracovas ◽  
Valéria S. Gonçalves ◽  
Cláudio José da Rocha ◽  
Ricardo Mendes Leal Neto
Keyword(s):  
Water Immersion ◽  
Control Agent ◽  
Milling Process ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Process Control Agent ◽  
Effective Dispersion ◽  
Powder Mass ◽  
Ignition And Combustion ◽  
Milled Powders

In this work shake milling were used to mechanically activate Nb – Al powder mixtures at different relative proportions (Nb80Al, Nb65Al, Nb54Al e Nb42Al). All milling process parameters were unchanged, e.g., powders mass, ball/powder mass ratio, balls diameter, quantity and kind of process control agent. Uniaxially compacted cylindrical pellets of milled powders were vacuum reacted. After a two-step degassing treatment (290°C for 0.5 h and 400°C for 4 h), samples were heated at 30°C/min. Ignition and combustion temperatures were measured by a thermocouple inserted in a hole drilled into the pellets. The microstructure of milled powders and reacted pellets were characterized by X-ray diffraction and SEM analysis. Bulk density of the pellets was measured by water immersion (Archimedes). The results showed a decrease of both ignition and combustion temperature with mechanical activation as seen by comparison with reacted pellets of the same composition not mechanically activated (simple mixtures). By increasing the heating hate the completeness of the reactions were improved. The lower the aluminum contents the lower the ignition and combustion temperatures and also the densification. The decrease on ignition temperature was caused by a more effective dispersion (and so more activation) attained by samples with lower aluminum content.

Synthesis of TiFe Compound from Ball Milled TiH2 and Fe Powders Mixtures

2014 ◽  
Vol 802 ◽  
pp. 61-65 ◽  
Author(s):  
Railson Bolsoni Falcão ◽  
Edgar Djalma Campos Carneiro Dammann ◽  
Cláudio José da Rocha ◽  
Rodrigo Uchida Ichikawa ◽  
Michelangelo Durazzo ◽  
...  
Keyword(s):  
Profile Analysis ◽  
High Vacuum ◽  
High Energy ◽  
Planetary Mill ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
Sample Number ◽  
Heat Treated ◽  
Crystallite Sizes ◽  
Energy Ball

TiFe compound was produced by high-energy ball milling of TiH2and Fe powders, followed by heating under vacuum. TiH2was used instead of Ti in order to avoid the strong particles adhesion to grinding balls and vial walls. Mixtures of TiH2and Fe powders were dry-milled in a planetary mill for times ranging from 5 to 40 hours. The amount of sample, number and diameter of the balls were kept constant in all experiments. After milling, samples were heated under dynamic high-vacuum for the synthesis reaction. As-milled and heat-treated materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The mean crystallite sizes and microstrains were determined by XRD line profile analysis using the Warren-Averbach method. As-milled materials presented only Fe and TiH2phases. Nanostructured TiFe compound was formed after heat treatment. TiH2was effective for providing low adherence of the powders during milling.

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