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.

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.

scholarly journals Formation of Intermediate Phases and Supersaturated Solid Solution in Al-Cu System during Diffusion

2018 ◽  
Vol 383 ◽  
pp. 31-35 ◽  
Author(s):  
Alexey Rodin ◽  
Nataliya Goreslavets
Keyword(s):  
Phase Diagram ◽  
Solid Solution ◽  
High Temperature ◽  
Chemical Composition ◽  
Low Temperature ◽  
Supersaturated Solid Solution ◽  
Diffusion Processes ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Intermediate Phases

The study of diffusion processes in the aluminum - copper system was carried out at the temperature 350 and 520 °C. Special attention was paid on the chemical composition of the system near Al/Cu interface. It was determined that the intermediate phases in the system, corresponding to the equilibrium phase diagram, were not formed at low temperature. At high temperature the intermediate phases forms starting with Cu - rich phases. In both cases supersaturated solid solution of copper in aluminum could be observed near the interface.

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.

scholarly journals Early stages of solid state reactions: insights from micro-XRD and XAS

2014 ◽  
Vol 70 (a1) ◽  
pp. C1519-C1519
Author(s):  
Serena Tarantino ◽  
Paolo Ghigna ◽  
Elisabetta Achilli ◽  
Sonia Pin ◽  
Michele Zema ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Solid State ◽  
Equilibrium Phase ◽  
Experimental System ◽  
Equilibrium Phase Diagram ◽  
Solid State Reactions ◽  
Reactive System ◽  
X Ray ◽  
Early Stages ◽  
Intermediate Phases

The mechanism of a solid state reaction in its early stages can be explored by investigating the time evolution of a model reactive system made of a thin layer of one reagent deposited onto a single crystal slab of the other reagent. Insights can be retrieved by comparing results at both local and long length scales obtained with films of different thicknesses and deposited onto different crystal orientations. In particular, reaction between ZnO and Al2O3has been chosen, as the spinel-forming reactions have been and still remain a model experimental system for investigating solid state reactions and because in the ZnO/Al2O3phase diagram, spinel is the only stable compound. The reaction initial steps have been investigated by using synchrotron X-ray diffraction, atomic force microscopy and X-ray absorption spectroscopy at the Zn-K edge starting from zincite films deposited onto (110)-, (012)-, (001)-oriented corundum single crystals [1,2]. The reaction eventually yields ZnAl2O4spinel but via a complex mechanism involving side and intermediate non-equilibrium compounds that do not appear in the equilibrium phase diagram of the pseudo-binary system. Spinel, when occurs, is polycrystalline at the end but initially forms with a few preferred orientations. Intermediate phases form before and in parallel with the growth of the spinel. Their number, composition, structure and kinetic role strongly depend on substrate orientation and film thickness. A more detailed understanding of the reactivity can be inferred by comparing EXAFS results to those of grazing incidence diffraction experiments of the films deposited on the (001) face of Al2O3and heat-treated at 10000C for different lengths of time. Information on the structure of the intermediate phases is given and results are discussed by comparing different films thickness to clarify the role of interfacial free energy and crystallographic orientation.

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.

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