Enhancement of the Order/Disorder Reaction in Fe-Ni

Radiation Induced ◽

Kinetics Of ◽

Fcc Structure

The Fe-Ni phase diagram is not well understood below 400°C. Of particular interest in this region is a disorder to order reaction whereby Fe-50 wt% Ni transforms from an FCC structure to an L1o superstructure. The kinetics of this transformation, however, are extremely slow (Table I). Therefore, to observe low-temperature transformations in the Fe-Ni system, extremely slow-cooled alloys must be studied (e.g., meteorites) or diffusion must be enhanced. One method to speed diffusion is irradiation. In 1962 Fe-50 wt% Ni was neutron irradiated; electrical resistivity measurements revealed a critical temperature (Tc)of 320°C. In 1977 Fe-50 wt% Ni was irradiated on a high voltage electron microscope (HVEM) and a T of 320°C was again found. A question arises, however, whether radiation enhanced diffusion or whether the radiation induced the transformation, causing a non-equilibrium ordered phase to form.

Atomic Transport in Irradiated Solids

MRS Proceedings ◽

10.1557/proc-311-209 ◽

1993 ◽

Vol 311 ◽

Author(s):

R.R. Averback ◽

Mai Ghaly ◽

Y.Y. Lee ◽

H. Zhu

Keyword(s):

Ion Beam ◽

Rapid Quenching ◽

Primary Role ◽

Melting Points ◽

Crystalline Materials ◽

Enhanced Diffusion ◽

Atomic Transport ◽

Radiation Induced ◽

Kinetics Of

ABSTRACTAtomic transport in irradiated solids has been investigated in both the prompt and delayed regimes. Prompt effects are revealed on an atomic level through molecular dynamics computer simulations. It is demonstrated that for metals like gold, which have high atomic numbers and low melting points, thermal spikes play a primary role in the cascade dynamics and that concepts like melting and rapid quenching are useful descriptions. Surface effects in these metals are also discussed. For metals with higher melting points and lower atomic numbers, the cascade dynamics are determined almost exclusively by energetic collisions far above thermal energies. This is illustrated by simulations of cascades in NiAl. The effect of the high ordering energy in this intermetallic compound on the radiation-induced defect structure has also been studied.Atomic transport in the delayed regime is illustrated by two examples: an order-disorder alloy, Cu3Au, and an amorphous alloy, NiZr. The first example is used to illustrate various aspects of radiation enhanced diffusion (RED): ion beam mixing, diffusion kinetics, the effects of primary recoil spectrum, and the importance of chemical order. The second example illustrates that the basic theory of RED, which was developed to describe crystalline materials, appears to work adequately for amorphous metal alloys, suggesting that similar mechanisms may be operating. It is shown, however, that the kinetics of RED observed in amorphous alloys are not unique to point defect models.

Short and Long-Range Ordering of (Ni0.67Cr0.33)1-xFex Alloys Under Electron Irradiation

MRS Proceedings ◽

10.1557/proc-439-373 ◽

1996 ◽

Vol 439 ◽

Cited By ~ 2

Author(s):

E. Frely ◽

B. Beuneu ◽

A. Barbu ◽

G. Jaskierowicz

Keyword(s):

Electron Microscope ◽

Transition Temperature ◽

Long Range ◽

Model Alloy ◽

Resistivity Measurements ◽

Voltage Electron ◽

Superlattice Peak ◽

Long Range Ordering ◽

Kinetics Of

Abstract(Ni0.67Cr0.33)1-xFex alloys with x = 0, 5 and 10 at.%, have been irradiated at temperatures between 300°C and 500°C with the electrons of a 2.5MeV Van de Graaff accelerator and of a 1MeV High Voltage Electron Microscope (HVEM). All of them have been successively ordered at short and at long range under irradiation. The transition temperature is 525°C for Ni0.61Cr0.34Fe0.05 and 445°C for Ni0.59Cr0.31Fe0.10. An Inconel sample irradiated up to 1 d.p.a. in the 1MeV microscope did not show any superlattice peak although its composition is very close to the 10% iron model alloy. The kinetics of ordering has been followed by resistivity measurements and fitted by the Dienes kinetic model.

Mechanisms and Kinetics of Iion Beam-Induced Compositional Modifications

MRS Proceedings ◽

10.1557/proc-100-29 ◽

1988 ◽

Vol 100 ◽

Cited By ~ 4

Author(s):

N. Q. Lam

Keyword(s):

Synergistic Effects ◽

Relative Significance ◽

Near Surface ◽

Enhanced Diffusion ◽

Thermally Activated ◽

Target Composition ◽

Radiation Induced ◽

The Individual ◽

Kinetics Of

ABSTRACTNear-surface compositional modification of ion-bombarded alloys results from the dynamic interplay of several atomistic processes. In addition to displacement mixing leading to t randomization of atomic locations, which is dominant at relatively low temperatures, and preferential loss of alloying elements by sputtering, many thermally-activated processes, including radiation-enhanced diffusion, radiation-induced segregation and Gibbsian adsorption, also play important roles. The relative contributions of these processes to the evolution of the target composition profile depends on the target materials and irradiation variables. Although a good understanding of the individual processes has been achieved, information regarding their synergistic effects on alloy surface modification is still limited. In the present article, these processes will be characterized in simple physical terms, and the present understanding of their relative significance and contributions in changing the target composition during ion bombardment will be discussed in view of recent progress in theoretical modeling and experimental study.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107484 ◽

1978 ◽

Vol 36 (1) ◽

pp. 68-69

Author(s):

W. E. King

Keyword(s):

Electrical Resistivity ◽

Electron Microscope ◽

High Voltage ◽

Resistivity Measurements ◽

Voltage Electron ◽

High Voltage Electron ◽

Wide Range ◽

Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Measuring Radiation Enhanced Diffusion Through in situ Ion Radiation Induced Sintering of Oxide Nanoparticles

SSRN Electronic Journal ◽

10.2139/ssrn.3951050 ◽

2021 ◽

Author(s):

Nathan J. Madden ◽

Samuel A. Briggs ◽

Diana Perales ◽

Timothy J. Boyle ◽

Khalid Hattar ◽

...

Keyword(s):

Oxide Nanoparticles ◽

Enhanced Diffusion ◽

Radiation Induced

Modification of μm Thick Surface Layers Using keV Ion Energies

MRS Proceedings ◽

10.1557/proc-27-37 ◽

1983 ◽

Vol 27 ◽

Cited By ~ 2

Author(s):

L. E. Rehn ◽

N. Q. Lam ◽

H. Wiedersich

Keyword(s):

Elevated Temperature ◽

Elevated Temperatures ◽

Diffusion Processes ◽

Experimental Studies ◽

Surface Layers ◽

Enhanced Diffusion ◽

Ni Alloy ◽

Ion Energies ◽

Radiation Induced

ABSTRACTRoot-mean-square diffusion distances for both vacancy and interstitial defects in metals can be very large at elevated temperatures, e.g. several μm's in one second at 500°C. Consequently, defects that escape the implanted region at elevated temperature can produce compositional and microstructural changes to depths which are much larger than the ion range. Because of the high defect mobilities, and of the fact that diffusion processes must compete with the rate of surface recession, the effects of defect production (ballistic mixing), radiation-enhanced diffusion and radiation- induced segregation become spatially separated during ion bombardment at elevated temperature. Results of such experimental studies in a Cu-Ni alloy are presented, discussed and compared with predictions of a phenomenological model. Contributions to the subsurface compositional changes from radiation-enhanced diffusion and radiation- induced segregation are clearly identified.

Radiation-Induced Processes in Experiments Carried out In-situ in the High-Voltage Electron Microscope

10.1515/9783112472927-015 ◽

1979 ◽

pp. 157-168

Author(s):

K. Urban

Keyword(s):

Electron Microscope ◽

High Voltage ◽

Voltage Electron ◽

High Voltage Electron ◽

Radiation Induced

Prediction of High Dose Ion Implantation Profiles as Influenced by Radiation Induced Transport and Sputtering

MRS Proceedings ◽

10.1557/proc-45-91 ◽

1985 ◽

Vol 45 ◽

Cited By ~ 1

Author(s):

M. Rangaswamy ◽

D. Farkas

Keyword(s):

Probability Distributions ◽

Practical Interest ◽

High Dose ◽

High Fluence ◽

Enhanced Diffusion ◽

Preferential Sputtering ◽

Defect Probability ◽

Radiation Induced ◽

Effects Of Radiation

ABSTRACTVarious models for predicting high fluence ion collection profiles are reviewed. Recent calculations based on the diffusion approximation are described. The solute and defect probability distributions are calculated by a MONTECARLO code, TRIM. The method takes into account the effects of sputtering, including preferential sputtering of one of the components, and lattice dilation. In addition, the effects of radiation enhanced diffusion and radiation induced segregation are also considered. The calculations include the coupling of solute and defect fluxes. The described formalism can account for observed maximum attainable concentrations and distributions in high fluence implantation conditions of practical interest.