Analytical electron microscopy of aluminum ion-implanted with molybdenum

1983 ◽  
Vol 41 ◽  
pp. 262-263
Author(s):  
L. D. Stephenson ◽  
J. Bentley ◽  
R. B. Benson ◽  
P. A. Parrish
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Analytical Electron Microscopy ◽  
Microstructural Characterization ◽  
Equilibrium Phase Diagram ◽  
Naval Research ◽  
Aluminum Ion ◽  
Projected Range ◽  
Metastable Phase Formation ◽  
Ion Implanted

The microstructures of aluminum ion-implanted with molybdenum and subjected to various heat treatments are being investigated for correlation with nearsurface properties such as corrosion. Previous work indicated enhanced corrosion resistance, but dealt chiefly with the as-implanted condition and involved little microstructural characterization. In addition, the Al-Mo binary system is of interest because metastable phase formation was considered to be possible and the equilibrium phase diagram is poorly defined. Electropolished coupons 38 × 28 × 0.5 mm of 99.999% A1 with ∽0.5 mm grain size were implanted with Mo+ ions at the Naval Research Laboratory. The dual energy implant schedule of 4.88 × 1019 ions/m2 at 50 keV plus 6.14 × 1019 ions/m2 at 110 keV resulted in a peak concentration of 4.4 at. % Mo (measured by ion backscattering) within the projected range of ∽50 nm.Disks (3 imi diam) were electrodischarge machined from as-implanted specimens and then were backthinned by electropolishing.

In situ annealing of aluminum ion-implanted with molybdenum

1983 ◽  
Vol 41 ◽  
pp. 260-261
Author(s):  
J. Bentley ◽  
L. D. Stephenson ◽  
R. B. Benson ◽  
P. A. Parrish
Keyword(s):  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Naval Research ◽  
Dislocation Network ◽  
Dislocation Loops ◽  
High Concentration ◽  
Aluminum Ion ◽  
Ion Implanted

As part of an analytical electron microscopy study of aluminum ion-implanted with molybdenum, in situ annealing experiments have been performed to better understand the phase transformation mechanisms in material with a peak molybdenum content of approximately 11 at. % Mo. Ion implantations were performed at the Naval Research Laboratory on electropolished coupons 38 × 28 × 0.5 mm of 99.999% Al with 0.5 mm grain size. A dual energy implant schedule of 1.12 × 1020 ions/m2 at 50 keV. plus 1.24 × 1020 ions/m2 at 110 keV was employed. The TEM specimens were prepared by electrodischarge machining 3-mm diameter disks from the implanted coupons and backthinning by electropolishing. In situ annealing was performed in a Philips EM 400T/FEG with the use of a Philips single-tilt heating holder. Videotape recordings were made from the TEM fluorescent viewing screen in the tilted position.A high concentration of small dislocation loops and possibly a tangled dislocation network were present in the as-implanted material. No precipitates were observed; this is consistent with a supersaturated solid solution.

High Power Laser Effects on Unimplanted and Implanted Aluminium Single Crystals

1980 ◽  
Vol 1 ◽  
Author(s):  
G. Battaglin ◽  
A. Carnera ◽  
G. Della Mea ◽  
P. Mazzoldi ◽  
A.K. Jain ◽  
...  
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Front Velocity ◽  
Segregation Coefficient ◽  
Power Laser ◽  
Intermediate Phases ◽  
Metastable Phase Formation ◽  
Nonequilibrium Effects ◽  
Equilibrium Segregation

Mechanisms involved in laser processing of ion implanted semiconductors have been extensively investigated (1,2). Relatively little work has been done on implanted metals (3,10). The liquid solid interface (melt front) velocity in metals (11,12) is much larger than that in Si. Therefore several nonequilibrium effects on recrystallization (6) solute segregation (9) and metastable phase formation (4,6,7) are observed. Such effects would depend on the melt front velocity, equilibrium phase diagram considerations (such as equilibrium segregation coefficient Ko, miscibility in licuid phase, intermediate phases etc.) and also on the as implanted nonequilibrium phase and defect structure. In this paper we present a study of the influence of some of these parameters during laser treatment of sincle crystals of virgin Al and dilute implanted alloys of Mo and Cd in Al.

Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films

1991 ◽  
Vol 230 ◽  
Author(s):  
J. B. Rubin ◽  
R. B. Schwarz
Keyword(s):  
Thin Films ◽  
Cooling Rate ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Amorphous Structure ◽  
Nucleation Theory ◽  
Glass Forming ◽  
Constant Heating

AbstractWe determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.

Phase Stability and Interface Reactions in the Al-SiC System

1988 ◽  
Vol 120 ◽  
Author(s):  
Doh-Jae Lee ◽  
Mark D. Vaudin ◽  
Carol A. Handwerker ◽  
Ursula R. Kattner
Keyword(s):  
Phase Diagram ◽  
Phase Stability ◽  
Equilibrium Phase ◽  
Analytical Electron Microscopy ◽  
Equilibrium Phase Diagram ◽  
Grain Structure ◽  
Particulate Composites ◽  
Matrix Composites ◽  
Interface Reactions ◽  
Analytical Electron

AbstractThe Al-SiC system has been used as a model system in an examination of phase stability in the presence of a liquid phase and microstructure development in metal-matrix composites. The Al-Si-C phase diagram has been calculated for temperatures between 500°C and 1500°C. The phases formed between Al(liquid) and SiC at 920°C have been determined experimentally, using analytical electron microscopy, in both fiber and particulate composites and compared with what is predicted from the equilibrium phase diagram. The morphologies and the spatial distributions of phases have also been examined in addition to the phase analysis. The only phases found were Al, Al4C3, SiC, and Si. Although Al4SiC4 is calculated to be stable at 920°C, it was not found. The SiC grain structure was found to influence strongly the morphology of the Al4C3-SiC and Al-SiC interfaces.

scholarly journals Non-Equilibrium Processing of Ni-Si Alloys at High Undercooling and High Cooling Rates

2014 ◽  
Vol 790-791 ◽  
pp. 22-27 ◽  
Author(s):  
Andrew M. Mullis ◽  
Lei Gang Cao ◽  
Robert F. Cochrane
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Eutectic Structure ◽  
Eutectic Solidification ◽  
Drop Tube ◽  
High Undercooling ◽  
Cooling Rates ◽  
Β Phase ◽  
High Cooling Rates

Melt encasement (fluxing) and drop-tube techniques have been used to solidify a Ni-25 at.% Si alloy under conditions of high undercooling and high cooling rates respectively. During undercooling experiments a eutectic structure was observed, comprising alternating lamellae of single phase γ (Ni31Si12) and Ni-rich lamellae containing of a fine (200-400 nm) dispersion of β1-Ni3Si and α-Ni. This is contrary to the equilibrium phase diagram from which direct solidification to β-Ni3Si would be expected for undercoolings in excess of 53 K. Conversely, during drop-tube experiments a fine (50 nm) lamellar structure comprising alternating lamellae of the metastable phase Ni25Si9 and β1-Ni3Si is observed. This is also thought to be the result of primary eutectic solidification. Both observations would be consistent with the formation of the high temperature form of the β-phase (β2/β3) being suppressed from the melt.

THE METASTABLE PHASE DIAGRAM OF THE BLUME–EMERY–GRIFFITHS MODEL IN ADDITION TO THE EQUILIBRIUM PHASE DIAGRAM USING THE PAIR APPROXIMATION

2005 ◽  
Vol 19 (10) ◽  
pp. 1741-1755 ◽  
Author(s):  
AHMET ERDİNÇ ◽  
MUSTAFA KESKİN
Keyword(s):  
Phase Diagram ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Order Parameters ◽  
Second Order ◽  
Pair Approximation ◽  
Variation Method ◽  
Metastable Phase Diagram ◽  
Phase Boundaries

As a continuation of our previously published work, the metastable phase diagram of the Blume–Emery–Griffiths model with the arbitrary bilinear (J), biquadratic (K) and crystal field interaction (D) is presented in addition to the equilibrium phase diagram in (T/K, J/K) and (T/K, D/K) plane by using the pair approximation of the cluster variation method on a body centered cubic lattice. We also calculate the phase transitions for the unstable branches of order parameters. The calculated first- and second-order phase boundaries of the unstable branches of the order parameters are superimposed on the equilibrium phase diagram and metastable phase diagram. It is found that the metastable phase diagram and the first- and second-order phase boundaries for unstable branches of order parameters always exist at low temperatures, which are consistent with the experimental and theoretical works.

scholarly journals DFT-CEF Approach for the Thermodynamic Properties and Volume of Stable and Metastable Al–Ni Compounds

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1142
Author(s):  
Silvana Tumminello ◽  
Mauro Palumbo ◽  
Jörg Koßmann ◽  
Thomas Hammerschmidt ◽  
Paula R. Alonso ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Density Functional ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Configurational Entropy ◽  
Equilibrium Phase Diagram ◽  
Metastable Phases ◽  
Stability Range

The Al–Ni system has been intensively studied both experimentally and theoretically. Previous first-principles calculations based on density-functional theory (DFT) typically investigate the stable phases of this system in their experimental stoichiometry. In this work, we present DFT calculations for the Al–Ni system that cover stable and metastable phases across the whole composition range for each phase. The considered metastable phases are relevant for applications as they are observed in engineering alloys based on Al–Ni. To model the Gibbs energies of solid phases of the Al–Ni system, we combine our DFT calculations with the compound energy formalism (CEF) that takes the Bragg–Williams–Gorsky approximation for the configurational entropy. Our results indicate that the majority of the investigated configurations have negative energy of formation with respect to Al fcc and Ni fcc. The calculated molar volumes for all investigated phases show negative deviations from Zen’s law. The thermodynamic properties at finite temperatures of individual phases allow one to predict the configurational contributions to the Gibbs energy. By applying a fully predictive approach without excess parameters, an acceptable topology of the DFT-based equilibrium phase diagram is obtained at low and intermediate temperatures. Further contributions can be added to improve the predictability of the method, such as phonons or going beyond the Bragg–Williams–Gorsky approximation that overestimates the stability range of the ordered phases. This is clearly demonstrated in the fcc order/disorder predicted metastable phase diagram.

Structural studies of Al-based powders prepared by chemical methods

1992 ◽  
Vol 7 (9) ◽  
pp. 2418-2423 ◽  
Author(s):  
M. Lenarda ◽  
R. Ganzerla ◽  
L. Storaro ◽  
R. Frattini ◽  
S. Enzo
Keyword(s):  
Chemical Reduction ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Aluminum Hydride ◽  
Equilibrium Phase Diagram ◽  
Lithium Aluminum ◽  
Metal Powders ◽  
Nial Phase ◽  
Cobalt Acetylacetonate ◽  
Thermal Stability Of

Finely dispersed metal powders have been obtained after chemical reduction of Ni and Co acetylacetonate by lithium aluminum hydride in tetrahydrofuran at low temperature. The Al/Ni and Al/Co stoichiometry of the as-reduced powders was 1.1 and 1.2, respectively. The structure and thermal stability of the as-reduced powders were affected by the temperature of reduction. For the NiAl powders it was found that the thermal treatment initially induces a separation of highly unstable Ni(Al) and Al(Ni) solid solutions, which subsequently react to give a single NiAl phase of cubic structure not reported in the equilibrium phase diagram. Conversely, the reduction of cobalt acetylacetonate directly gives a cubic metastable phase, from which precipitates some hexagonal form of Co after treatment at 450 °C.

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