Ignition and combustion of mechanically alloyed Al–Mg powders with customized particle sizes

2013 ◽  
Vol 160 (4) ◽  
pp. 835-842 ◽  
Author(s):  
Yasmine Aly ◽  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Particle Sizes ◽  
Mechanically Alloyed ◽  
Ignition And Combustion

Preparation, ignition, and combustion of mechanically alloyed Al-Mg powders with customized particle sizes

2013 ◽  
Vol 1521 ◽  
Author(s):  
Yasmine Aly ◽  
Vern K. Hoffman ◽  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Particle Size ◽  
Ignition Delay ◽  
Pure Aluminum ◽  
Particle Morphology ◽  
Combustion Characteristics ◽  
Particle Sizes ◽  
Mechanically Alloyed ◽  
Pressurization Rate ◽  
Improved Performance ◽  
Ignition And Combustion

ABSTRACTAdding aluminum to propellants, pyrotechnics, and explosives is a common way to boost their energy density. A number of approaches have been investigated that shorten aluminum ignition delay, increase combustion rate, and decrease the tendency of aluminum droplets to agglomerate. Previous work showed that particles of mechanically alloyed Al-Mg powders burn faster than similarly sized particles of pure aluminum. However, preparation of mechanically alloyed powders with particle sizes matching those of fine aluminum used in energetic formulations was not achieved. This work is focused on preparation of mechanically alloyed, composite Al-Mg powders in which both internal structures and particle size distributions are adjusted. Binary powders with compositions in the range of 50 - 90 at. % Al were prepared and characterized. Milling protocol is optimized to prepare equiaxial, micron-scale particles suitable for laboratory evaluations of their oxidation, ignition, and combustion characteristics. Quantitative particle size analyses are done using low-angle laser light scattering. Electron microscopy and x-ray diffraction are used to examine particle morphology and phase makeup, respectively. Combustion of aerosolized powder clouds is studied using a constant volume explosion setup. For all materials, ignition and combustion characteristics are compared to each other and to those of pure Al. Compositions with improved performance (i.e., shorter ignition delay and faster pressurization rate) compared to pure Al are identified.

Reactive, Mechanically Alloyed Al·Mg Powders with Customized Particle Sizes and Compositions

2014 ◽  
Vol 30 (1) ◽  
pp. 96-104 ◽  
Author(s):  
Yasmine Aly ◽  
Vern K. Hoffman ◽  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Particle Sizes ◽  
Mechanically Alloyed

Nb-W Alloy Prepared by Mechanical Alloying and Optimal Design of Corresponding Milling Variables

2014 ◽  
Vol 1033-1034 ◽  
pp. 839-848
Author(s):  
Bai Ru Li ◽  
Yong Dong Wang ◽  
Xing Liu
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Particle Size ◽  
Milling Time ◽  
Milled Powder ◽  
Orthogonal Test ◽  
Particle Sizes ◽  
Liquid Ratio ◽  
Mechanically Alloyed ◽  
Fe Content

The effects of milling variables on the particle sizes and purity of mechanically alloyed Nb-30W powders were quantitatively investigated using orthogonal test of three factors consisting of milling time A (12h, 24h and 48h), ball-to-powder ratio B (6:1, 10:1 and 20:1) and solid-to-liquid ratio C (1:0.2, 1:0.5 and 1:1) at three levels in order to optimize the milling variables of mechanically alloyed Nb-30W powders. Results indicated that the particle size was mainly determined by the solid-to-liquid ratio and the purity of powder was mainly affected by the ball-to-powder ratio and the milling time; best combination of all variables was found to be A2B2C1 with the particle size 12.62μm and Fe content 0.399%. After hot pressed, A2B2C1 combination obtained the highest mechanical properties. With the refining of particles during milling, the Fe contaminations of milled powder increased and were dissolved into Nb lattices to form Nb (Fe) solid solution; meanwhile, macro stress caused by plastic deformation of Nb particles was released.

Investigation on Phase Evolution in Mechanically Alloyed Nano-Structured Fe-Si System

2013 ◽  
Vol 829 ◽  
pp. 703-706 ◽  
Author(s):  
Sara Torkan ◽  
Abolghasem Ataie ◽  
Hossein Abdizadeh
Keyword(s):  
Phase Composition ◽  
Mechanical Alloying ◽  
Rietveld Method ◽  
Phase Evolution ◽  
Particle Sizes ◽  
Mechanically Alloyed ◽  
Time Intervals ◽  
Nano Crystalline ◽  
Milled Sample ◽  
Powder Samples

In the present research, nano-crystalline Fe­70Si30alloy powders were prepared by mechanical alloying using Fe and Si powder as starting materials. Powder samples were taken from the mill at selected time intervals (5, 20, 40, 50, 60, 70h) for the structural properties analysis. The phase composition, morphology and magnetic properties of nano-structured alloy powders were analyzed by XRD, FESEM and VSM techniques, respectively. The evolution of non-equilibrium solid solution Fe (Si) during milling was accompanied by refinement of crystallite size. Dissolution of Si atoms into Fe matrix was also studied. The quantitative analysis of phase composition was carried out using Maud software which is based on the Rietveld method combined with Fourier analysis. XRD results showed a coexistence of BCC, DO3and FeSi structural phases for 40h milled sample, quantity of DO3and FeSi phases decreased for prolonged milling time. These phases disappeared in 60h milled sample and BCC FeSi phase with a mean crystallite and particle sizes of 20 and 70 nm were formed. The results also indicated that by mechanical alloying of the FeSi system for 60h, it was possible to extend the solubility of the BCC FeSi structure to 30 at% Si.

Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

1977 ◽  
Vol 35 ◽  
pp. 298-299
Author(s):  
Jordi Marti ◽  
Timothy E. Howson ◽  
David Kratz ◽  
John K. Tien
Keyword(s):  
Solid Solution ◽  
Volume Fraction ◽  
Stress Rupture ◽  
Oxide Dispersion Strengthened ◽  
Solid Solution Alloy ◽  
Oxide Dispersion ◽  
Creep And Stress Rupture ◽  
Mechanically Alloyed ◽  
Fine Microstructure ◽  
Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

Characterization of carbides in M50NiL

1991 ◽  
Vol 49 ◽  
pp. 606-607
Author(s):  
L. S. Lin ◽  
K. P. Gumz ◽  
A. V. Karg ◽  
C. C. Law
Keyword(s):  
Temperature Effects ◽  
Base Composition ◽  
Lattice Parameter ◽  
Control Surface ◽  
Carbide Formation ◽  
Particle Sizes ◽  
Low Carbon ◽  
Fee Structure ◽  
Heat Treated

Carbon and temperature effects on carbide formation in the carburized zone of M50NiL are of great importance because they can be used to control surface properties of bearings. A series of homogeneous alloys (with M50NiL as base composition) containing various levels of carbon in the range of 0.15% to 1.5% (in wt.%) and heat treated at temperatures between 650°C to 1100°C were selected for characterizations. Eleven samples were chosen for carbide characterization and chemical analysis and their identifications are listed in Table 1.Five different carbides consisting of M6C, M2C, M7C3 and M23C6 were found in all eleven samples examined as shown in Table 1. M6C carbides (with least carbon) were found to be the major carbide in low carbon alloys (<0.3% C) and their amounts decreased as the carbon content increased. In sample C (0.3% C), most particles (95%) encountered were M6C carbide with a particle sizes range between 0.05 to 0.25 um. The M6C carbide are enriched in both Mo and Fe and have a fee structure with lattice parameter a=1.105 nm (Figure 1).

TEM study on fine carbide precipitates and dislocation cell structure

1990 ◽  
Vol 48 (4) ◽  
pp. 904-905
Author(s):  
Mengzhe Chen ◽  
Siqin Wang ◽  
Jun Ke
Keyword(s):  
Carbide Particle ◽  
Cell Structure ◽  
Ferrite Matrix ◽  
Dislocation Cell ◽  
Isothermal Treatment ◽  
Particle Sizes ◽  
Dislocation Cell Structure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Fine Carbide

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.

Microstructure of mechanically alloyed and hot-pressed Al5CuZr2

1990 ◽  
Vol 48 (4) ◽  
pp. 970-971
Author(s):  
T. E. Mitchell ◽  
P. B. Desch ◽  
R. B. Schwarz
Keyword(s):  
Mechanical Alloying ◽  
Vickers Hardness ◽  
Hot Pressing ◽  
Rapid Quenching ◽  
Hardened Steel ◽  
Alloyed Powder ◽  
Ion Milling ◽  
Mechanical Grinding ◽  
Mechanically Alloyed ◽  
Steel Container

Al3Zr has the highest melting temperature (1580°C) among the tri-aluminide intermetal1ics. When prepared by casting, Al3Zr forms in the tetragonal DO23 structure but by rapid quenching or by mechanical alloying (MA) it can also be prepared in the metastable cubic L12 structure. The L12 structure can be stabilized to at least 1300°C by the addition of copper and other elements. We report a TEM study of the microstructure of bulk Al5CuZr2 prepared by hot pressing mechanically alloyed powder.MA was performed in a Spex 800 mixer using a hardened steel container and balls and adding hexane as a surfactant. Between 1.4 and 2.4 wt.% of the hexane decomposed during MA and was incorporated into the alloy. The mechanically alloyed powders were degassed in vacuum at 900°C. They were compacted in a ram press at 900°C into fully dense samples having Vickers hardness of 1025. TEM specimens were prepared by mechanical grinding followed by ion milling at 120 K. TEM was performed on a Philips CM30 at 300kV.

A High Resolution Study of Alumina Supported Iridium Catalysts

1980 ◽  
Vol 38 ◽  
pp. 202-203
Author(s):  
C. Stoeckert ◽  
B. Etherton ◽  
M. Beer ◽  
J. Gryder
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Metal Particles ◽  
Optical Transfer Function ◽  
Particle Sizes ◽  
Iridium Catalysts ◽  
Transmission Electron ◽  
Optical Transfer ◽  
Conventional Transmission Electron Microscope ◽  
Resolution Study

The interpretation of the activity of catalysts requires information about the sizes of the metal particles, since this has implications for the number of surface atoms available for reaction. To determine the particle dimensions we used a high resolution STEM1. Such an instrument with its simple optical transfer function is far more suitable than a conventional transmission electron microscope for the establishment of particle sizes. We report here our study on the size and number distribution of Ir particles supported on Al2O3 and also examine simple geometric models for the shape of Ir particles.

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