scholarly journals Precipitation and Growth Kinetics in Mechanically Alloyed Ni–Al

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
QingXin Tang ◽  
Shigeharu Ukai ◽  
Akinobu Minami ◽  
Shigenari Hayashi
Keyword(s):  
Growth Kinetics ◽  
Ostwald Ripening ◽  
Arrhenius Plot ◽  
Lattice Misfit ◽  
Oxide Dispersion Strengthened ◽  
Mechanically Alloyed ◽  
Spherical Type ◽  
Atom Diffusion ◽  
The Matrix ◽  
Kinetics Of

The precipitation and growth kinetics ofγ′ precipitates, which are strengthening factors in Ni-base oxide dispersion strengthened (ODS) superalloys, were investigated. The cuboidal-typeγ′ precipitates are formed in conventional arc-melted Ni–Al alloys, whereas spherical-type precipitates are formed in the mechanically alloyed (MAed) specimens. The morphology is controlled by a lattice misfit between theγ′ precipitates and the matrix at the aging temperature of 800°C. The growth kinetics of theγ′ precipitates can be followed by Ostwald ripening. The Arrhenius plot yielded a lower activation energy for the solute atom diffusion in MAed specimens, which is attributed to their high dislocation density and nanosized grains.

Growth Kinetics of Quantum Size ZnO Particles

1998 ◽  
Vol 536 ◽  
Author(s):  
E. M. Wong ◽  
J. E. Bonevich ◽  
P. C. Searson
Keyword(s):  
Growth Kinetics ◽  
Ostwald Ripening ◽  
Chemical Potential ◽  
Colloidal Suspensions ◽  
Green Emission ◽  
Blue Shift ◽  
Constant Current ◽  
Mass Model ◽  
Zno Particles ◽  
Kinetics Of

AbstractColloidal chemistry techniques were used to synthesize ZnO particles in the nanometer size regime. The particle aging kinetics were determined by monitoring the optical band edge absorption and using the effective mass model to approximate the particle size as a function of time. We show that the growth kinetics of the ZnO particles follow the Lifshitz, Slyozov, Wagner theory for Ostwald ripening. In this model, the higher curvature and hence chemical potential of smaller particles provides a driving force for dissolution. The larger particles continue to grow by diffusion limited transport of species dissolved in solution. Thin films were fabricated by constant current electrophoretic deposition (EPD) of the ZnO quantum particles from these colloidal suspensions. All the films exhibited a blue shift relative to the characteristic green emission associated with bulk ZnO. The optical characteristics of the particles in the colloidal suspensions were found to translate to the films.

Pore growth kinetics in heat-treated glass-like carbons

1986 ◽  
Vol 1 (6) ◽  
pp. 832-835 ◽  
Author(s):  
Jalil Lachter ◽  
Leo G. Henry ◽  
Robert H. Bragg ◽  
Stephen Spooner
Keyword(s):  
Growth Kinetics ◽  
Matrix Material ◽  
Radius Of Gyration ◽  
Void Size ◽  
Kcal Mole ◽  
X Ray ◽  
X Ray Scattering ◽  
Heat Treated ◽  
The Matrix ◽  
Kinetics Of

The kinetics of changes in void size during annealing of glass-like carbons in the temperature range 1000°−2800 °C for times up to 150 h were studied using small-angle x-ray scattering determinations of the radius of gyration Rg. The results show that Rg ranged from 9 Å at 1000°C to about 24 Å at 2800 °C. A pore coarsening analysis and a superimposition kinetic analysis applied to Rg gave activation energies of 76 ± 4 kcal/mole and 74 ± 9 kcal/mole, respectively, which are associated with migration of vacancies within graphitic layers in the matrix material.

Phase Decomposition in Isothermally Aged MA Cu-Ni-Fe and Cu-Ni-Cr Alloys

2006 ◽  
Vol 15-17 ◽  
pp. 678-683 ◽  
Author(s):  
Felipe Hernandez-Santiago ◽  
I. Espinoza-Ramirez ◽  
Victor M. Lopez-Hirata ◽  
Maribel L. Saucedo-Muñoz ◽  
Lucia Díaz-Barriga Arceo ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Growth Kinetics ◽  
Phase Decomposition ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Composition Modulation ◽  
Diffusion Controlled ◽  
Supersaturated Solid Solutions ◽  
Kinetics Of ◽  
Modulation Wavelength

Supersaturated solid solutions of Cu-44.5at.%Ni-22.5at.%Fe and Cu-37at.%Ni-6at.%Cr alloy were produced by ball milling of a pure chemical elemental mixture for 1080 ks. Two fcc supersaturated solid solutions with a grain size of about 20 and 50 nm, respectively, were obtained after milling. These alloys were subsequently aged at temperatures between 800 and 1003 K for different times. The aging promoted the phase decomposition of the supersaturated solid solution into a mixture of Cu-rich and Ni- phases in both the aged MA alloy powders. The growth kinetics of the modulation wavelength was determined from the X-ray diffraction results and followed the Lifshitz-Slyozov- Wagner theory for a diffusion-controlled coarsening in the mechanically-alloyed Cu-Ni-Fe alloy after aging. However, the sidebands intensity seems to be very low and overlapped with the peaks corresponding to the Cu-rich phase in the aged mechanically-alloyed Cu-Ni-Cr alloy. The growth kinetics of composition modulation wavelength for the aged MA Cu-Ni-Fe alloy was faster at 803 and 898 K than that for the same alloy composition obtained by a conventional processing and then aged at the same temperatures.

Preparation and Thermal Stability of a Mechanically Alloyed Oxide Dispersion Strengthened Ferritic Steels

2012 ◽  
Vol 715-716 ◽  
pp. 605-610
Author(s):  
Yu Ren Wen ◽  
Yong Liu ◽  
Dong Hua Liu ◽  
Bei Tang
Keyword(s):  
Thermal Stability ◽  
Nuclear Power ◽  
Oxygen Carrier ◽  
Milled Powder ◽  
Oxide Dispersion Strengthened ◽  
Average Diameter ◽  
Ferritic Steels ◽  
Oxide Dispersion ◽  
Mechanically Alloyed ◽  
The Matrix

Oxide dispersion strengthened ferritic steels (so-called nanostructured ferritic alloys, NFAs), which are candidate structural materials in next generation nuclear power plant, have attracted much attention during recent years. In this work, iron oxide as oxygen carrier and titanium, yttrium hydrides were together mechanically milled with Fe-14Cr-3W gas-atomized powder. The thermal stability and recrystallization behaviour of the as-milled ferritic powder were studied by means of metallography, SEM, TEM and microhardness test. After ball milling for 48h, complete solid solution of bcc-Fe was formed in the as-milled powder. The thermal analysis results show that dispersed oxides with an average diameter of 5nm precipitate from the supersaturated matrix at about 850 °C. During annealing at temperatures from 800 to 1000 °C, a large number of equiaxed grains as fine as few hundreds of microns were found embedding in the matrix; the recrystallized grains stay quite stable and show minor dependence on annealing temperature and time. After being heated to 1200 °C for extended time, abnormal grain growth took place and resulted in bimodal grained structure. The effect of secondary particles on the thermal stability and recrystallization behavior of the ferritic steel was also discussed.

On the Diffusivity of Au in Pb

1985 ◽  
Vol 57 ◽  
Author(s):  
Ann N. Campbell ◽  
David Turnbull
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Ostwald Ripening ◽  
Second Phase ◽  
Precipitate Phase ◽  
Tracer Diffusivity ◽  
Interstitial Defect ◽  
The Matrix ◽  
Kinetics Of ◽  
Good Agreement

AbstractThe precipitation of Pb3Au from dilute Pb(Au) alloys and the subsequent Ostwald ripening of the precipitate phase have been studied. The Au diffusivity which limits the precipitation from Pb(500 at. ppm Au) specimens is in good agreement with Dp = 45 exp[(−20.8 kcal/mol)/RT], found previously to control the precipitation rate in Pb(900–1000 at. ppm Au) alloys (Rossolimo and Turnbull, 1973). In contrast, precipitation from Pb(100 at. ppm Au) alloys and Ostwald ripening in the Pb(500 at. ppm Au) specimens appear to be governed by the high temperature Au tracer diffusivity, DAu = 0.0041 exp[(−9.35 kcal/mol)/RT], which is about 103 times greater than Dp at the temperatures of interest, 75 to 112°C, and is attributed to the motion of a Au interstitial defect. In the 100 ppm alloys the Au is incorporated most easily at the ends of the Pb3Au crystals and a ribbon- or whisker-like morphology results. The particles which form at the grain boundaries in the 500 ppm Au alloy specimens are at least six times larger in volume than the matrix particles and ripen at their expense. The Ostwald ripening kinetics of the grain boundary particles scale with t1/2 rather than with t1/3 as is usual. The Pb3Au formed whiskers, blades, ribbons, or equiaxed particles depending upon the Au concentration and precipitation temperature. The precipitation and ripening kinetics are critically dependent on the morphology of the second phase.

scholarly journals Ostwald Ripening of Nanodispersed Phases in Metal Alloys (review)

2019 ◽  
Vol 20 (2) ◽  
pp. 101-119
Author(s):  
R.D. Vengrenovich ◽  
B.V. Ivanskii ◽  
M.O. Stasyk ◽  
S.V. Yarema ◽  
A.V. Moskaliuk ◽  
...  
Keyword(s):  
Ostwald Ripening ◽  
Theoretical Data ◽  
Metal Alloys ◽  
Practical Implementation ◽  
Matrix Diffusion ◽  
Mechanical Loads ◽  
Temperature Regimes ◽  
The Matrix ◽  
Kinetics Of ◽  
Mechanism Of Growth

The review deals with analysis of the kinetics of Ostwald ripening of nanodispersed phases in metal alloys when the growth (dissolution) of the nanoparticles of the reinforcing phase is controlled simultaneously by the  matrix diffusion, diffusion through the dislocation tubes and the rate of the atoms transition through the interphase boundary (Wagner's mechanism of growth). As a rule, different mechanisms of the nanoparticles growth (dissolution) are simultaneously employed in the process of the particles ripening while the number of the mechanisms involved in the growth (one, two or three) depends on various factors such as: chemical composition of the nanodispersed phases, conditions of exploitation (changes in mechanical loads, temperature regimes, environmental conditions), technological conditions of synthesis, etc. The possibility of practical implementation of the proposed mechanisms of growth of nanoparticles in the Ostwald ripening process can be confirmed or declined by a comparison between the experimental and theoretical data. As seen from the comparison between some experimental histograms with the lines built theoretically, the proposed mechanisms of growth of the dispersed phase nanoparticles seem realistic.

scholarly journals Structural evolution and grain growth kinetics of the mechanically alloyed Fe42.5Al42.5Ti5B10 induced by annealing

2008 ◽  
Vol 57 (9) ◽  
pp. 5774
Author(s):  
Ren Rong ◽  
Wu Yu-Cheng ◽  
Tang Wen-Ming ◽  
Wang Feng-Tao ◽  
Zheng Zhi-Xiang
Keyword(s):  
Grain Growth ◽  
Growth Kinetics ◽  
Structural Evolution ◽  
Mechanically Alloyed ◽  
Grain Growth Kinetics ◽  
Kinetics Of
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