Alternative Crystallization Phases in Sub-Micron Droplets of Fe-Ni Alloys

1985 ◽  
Vol 43 ◽  
pp. 46-47
Author(s):  
Yeon-Wook Kim ◽  
Thomas F. Kelly
Keyword(s):  
Liquidus Temperature ◽  
Metastable Phase ◽  
Phase 1 ◽  
Primary Crystallization ◽  
Supercooled Liquid ◽  
Nucleation Temperature ◽  
Crystal Phase ◽  
Liquid Volume ◽  
Ni Alloys ◽  
Crystal Phases

When a liquid becomes highly supercooled, the crystal phases that nucleate from it may be one of several alternatives other than the primary crystallization phase. Even though these crystal phases would be metastable at the liquidus temperature of the primary crystallization phase, they may or may not be the most stable crystal phase at the nucleation temperature. Thus the term “metastable phase” is not generally applicable and the name “alternative crystallization phase” (ACP) is used.In order to determine whether a particular crystal phase may nucleate in a supercooled liquid, it is not sufficient to determine simply which phase has the greater liquidus temperature. The effect of liquid supercooling (relative to the liquidus temperature of each phase) on the nucleation of each possible phase must be considered. For a given situation (eg. liquid volume, cooling rate,…), the propensity of a given phase for nucleating from the supercooled liquid can be gauged by calculating a nucleation temperature for that phase [1].

scholarly journals Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120263 ◽  
Author(s):  
H. N. W. Lekkerkerker ◽  
G. J. Vroege
Keyword(s):  
Phase Transitions ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Colloidal Suspensions ◽  
Crystal Phase ◽  
Liquid Crystal Phase ◽  
Future Developments ◽  
Mineral Particles ◽  
Crystal Phases ◽  
Liquid Crystal Phases

A review is given of the field of mineral colloidal liquid crystals : liquid crystal phases formed by individual mineral particles within colloidal suspensions. Starting from their discovery in the 1920s, we discuss developments on the levels of both fundamentals and applications. We conclude by highlighting some promising results from recent years, which may point the way towards future developments.

Refinement of Size Distributions for Primary Crystallizations

1997 ◽  
Vol 481 ◽  
Author(s):  
E. Pineda ◽  
T. Pradell ◽  
D. Crespo ◽  
N. Clavaguera ◽  
J. ZHU ◽  
...  
Keyword(s):  
Grain Size ◽  
Metastable Phase ◽  
Primary Crystallization ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Average Grain Size ◽  
Soft Impingement ◽  
Single Grain ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.

Crystal phase-dependent electrocatalytic hydrogen evolution performance of ruthenium–boron intermetallics

2020 ◽  
Vol 56 (20) ◽  
pp. 3061-3064 ◽  
Author(s):  
Xu Zou ◽  
Lina Wang ◽  
Xuan Ai ◽  
Hui Chen ◽  
Xiaoxin Zou
Keyword(s):  
Hydrogen Evolution ◽  
Crystal Phase ◽  
Crystal Phases ◽  
Activity Trends

Four crystal phases of ruthenium–boron intermetallics, including Ru7B3, RuB, Ru2B3 and RuB2, are selectively synthesized and their activity trends toward the HER are investigated.

scholarly journals Mechanical Modification of Al-6%Si By Semisolid Process

2016 ◽  
Vol 61 (3) ◽  
pp. 1689-1696
Author(s):  
Z. Sarajan
Keyword(s):  
Mechanical Property ◽  
Growth Temperature ◽  
Liquidus Temperature ◽  
Microstructure Characterization ◽  
Nucleation Temperature ◽  
Nucleation Event ◽  
Semisolid Processing ◽  
Globule Size ◽  
Semisolid Process

Abstract In this study by semisolid processing of Al-6%Si alloy, it has been found that small additions of Ti-6Al-4V shift the liquidus temperature up and the recalescence decreases. The nucleation event takes place at higher temperatures. Furthermore, the rate at which growth temperature increases is less than that of nucleation temperature and therefore more nuclei form with less potential for growth. In this processing refiner increases the α-Al percentage and reduces globule size. Improvement of mechanical property and microstructure characterization are the main advantages of this study.

Crystal phase effect upon O2 activation on gold surfaces through intrinsic strain

Nanoscale ◽  
2019 ◽  
Vol 11 (31) ◽  
pp. 14587-14591 ◽  
Author(s):  
Lixiang Zhong ◽  
Shuzhou Li
Keyword(s):  
Crystal Phase ◽  
Gold Surfaces ◽  
Phase Effect ◽  
O2 Activation ◽  
Crystal Phases ◽  
Intrinsic Strain

Different crystal phases have remarkably different surface reactivities due to their distinct intrinsic surface strains even for close-packed surfaces.

Glass Formation and Phase Separation In The Vitreloy Type Bulk Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
Charles C. Hays ◽  
Paul Kim ◽  
William L. Johnson
Keyword(s):  
Phase Separation ◽  
Liquid State ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Alloy System ◽  
Structural Data ◽  
Primary Crystallization ◽  
Supercooled Liquid ◽  
Glass Forming ◽  
Thermal Features

AbstractResults of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr-Ti-Cu-Ni-Be alloy system. The structural data identify the competing crystalline phases, formed on cooling from the liquid state, for various compositions in the Zr-Ti-X quasi-ternary phase diagram; with the Cu-Ni-Be ratio given by X = Be9Cu5Ni4. For this region of the ndimensional phase space (n=5), the bulk glass forming range is extensive and the calorimetric data exhibit thermal features associated with the occurrence of phase separation in the undercooled liquid state prior to primary crystallization. The topology of the composition manifold is complex; manifest by dramatic changes in crystallization behavior for small changes in the Zr-Ti-X ratio. Alloys with large supercooled liquid regions, Δ, are observed; ΔT≈ 135 K. Zr-Ti-Cu-Ni-Be alloy compositions with eutectic temperatures less than that of pure Al (Tm = 933 K) were also synthesized.

Crystallization Pathway in the Bulk Metallic Glass Zr41.2Ti13.8Cu12.5Ni10Be22.5

1996 ◽  
Vol 455 ◽  
Author(s):  
S. Schneider ◽  
P. Thiyagarajan ◽  
U. Geyer ◽  
W. L. Johnson
Keyword(s):  
Scattering Length ◽  
Primary Crystallization ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Amorphous Phases ◽  
New Family ◽  
Transmission Electron ◽  
Composition Fluctuations

AbstractA new family of multicomponent metallic alloys exhibits an excellent glass forming ability at moderate cooling rates of about 10K/s and a wide supercooled liquid region. These glasses are eutectic or nearly eutectic, thus far away from the compositions of competing crystalline phases. The nucleation of crystals from the homogeneous amorphous phase requires large thermally activated composition fluctuations for which the time scale is relatively long, even in the supercooled liquid. In the Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy therefore a different pathway to crystallization is observed. The initially homogeneous alloy separates into two amorphous phases. In the decomposed regions, crystallization probability increases and finally polymorphic crystallization occurs. The evolution of decomposition and succeeding primary crystallization in the bulk amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy have been studied by small angle neutron. Samples annealed isothermally in the supercooled liquid and in the solid state exhibit interference peaks indicating quasiperiodic inhomogeneities in the scattering length density. The related wavelengths increase with temperature according to the linear Cahn-Hilliard theory for spinodal decomposition. Also the time evolution of the interference peaks in the early stages is consistent with this theory. At later stages, X-ray diffraction and transmission electron microscopy investigations confirm the formation of nanocrystals in the decomposed regions.

Towards a True Fe-Ni Phase Diagram

1982 ◽  
Vol 21 ◽  
Author(s):  
P L. Rossiter ◽  
R. A Jago
Keyword(s):  
Phase Diagram ◽  
Phase Equilibrium ◽  
Phase Field ◽  
Metastable Phase ◽  
Equilibrium Diagram ◽  
Metastable Phase Diagram ◽  
Iron Meteorites ◽  
Slow Cooling ◽  
Ni Alloys ◽  
True Equilibrium

ABSTRACTA modification to the existing Fe-Ni phase equilibrium diagram is proposed that takes account of the low-temperature ordering reaction to FeNi. It is shown that true equilibrium is never attained during slow cooling of Fe-Ni alloys, even for iron meteorites (which cool extremely slowly). In all real cases, a metastable phase diagram applies, in which the depressed γ/α+γ solvus produces a more extensive γ+ FeNi phase field than for the equilibrium case. This enlarged phase field is used to explain the decomposition of supersaturated Fe-Ni to γ+ FeNi, which is observed only in iron meteorites.

Sign in / Sign up

Export Citation Format

Share Document