The Roles of Energetic Displacement Cascades in Ion Beam Modifications of Materials

1986 ◽  
Vol 74 ◽  
Author(s):  
R. S. Averback ◽  
S. -J. Kim ◽  
T. Diaz de la Rubia
Keyword(s):  
Point Defects ◽  
Elevated Temperatures ◽  
Ion Beam ◽  
Experimental Studies ◽  
Structural Disorder ◽  
Microstructural Development ◽  
Enhanced Diffusion ◽  
Displacement Cascades ◽  
Radiation Enhanced Diffusion ◽  
Cascade Processes

AbstractThe roles of energetic displacement cascades are ubiquitous in the fields of radiation damage and ion beam modifications of materials. These roles can be described on two time scales. For the first, which lasts ≈ 10-11 s, small cascade volumes are characterized by large supersaturations of point defects, structural disorder, and energy densities in excess of some tenths of eV's per atom. During this period, the system can be driven far from equilibrium with significant rearrangement of target atoms and the production of Frenkel pairs. Experimental studies of ion beam mixing in conjunction with molecular dynamics computer simulations, have contributed largely toward understanding these dynamic cascade processes. At later times, the microstructure of the material evolves as cascades begin to overlap, or at elevated temperatures, point defects migrate away from their nascent cascades. It will be shown how the primary state of damage in cascades influences this microstructural development. Examples involving radiation-enhanced diffusion and ion-induced amorphization will be discussed.

Modification of μm Thick Surface Layers Using keV Ion Energies

1983 ◽  
Vol 27 ◽  
Author(s):  
L. E. Rehn ◽  
N. Q. Lam ◽  
H. Wiedersich
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Diffusion Processes ◽  
Experimental Studies ◽  
Surface Layers ◽  
Enhanced Diffusion ◽  
Radiation 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.

High Energy Ion Beam Mixing in Al2 O3

1983 ◽  
Vol 27 ◽  
Author(s):  
M. B. Lewis ◽  
C. J. Mchargue
Keyword(s):  
Elevated Temperatures ◽  
Ion Beam ◽  
High Energy ◽  
Binary Collision ◽  
Surface Layers ◽  
Ion Beam Mixing ◽  
Enhanced Diffusion ◽  
Depth Profiles ◽  
Metal Atoms ◽  
Radiation Enhanced Diffusion

ABSTRACTThe ion beam mixing technique has been employed to mix metal atoms into the surface layers of Al2O3. Ion beams of Fe+ and Zr+ in the 1 to 4 MeV energy range were used to irradiate Al2O3 specimens on the surfaces of which films of chromium or zirconium had been evaporated. Some specimens were irradiated at elevated temperatures of 873 or 1173 K. Rutherford backscattering (RBS) and channeling methods were used to measure the metal atom depth profiles near the surface. Analyses of the backscattering data included binary collision calculations using the codes TRIM and MARLOWE. The significance and limitations of high energy (>1 MeV) beams for ion beam mixing experiments is discussed. Evidence was found for radiation enhanced diffusion and/or solubility of zirconium and chromium in Al2O3 at 873 K.

scholarly journals Reduction of Defect Fluxes Using Dual-Ion-Beam Processing

1993 ◽  
Vol 316 ◽  
Author(s):  
A. Iwase ◽  
L. E. Rehn ◽  
P. M. Baldo ◽  
P. R. Okamoto ◽  
H. Wiedersich ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Ion Beam ◽  
Beam Irradiation ◽  
Near Surface ◽  
Enhanced Diffusion ◽  
Dual Beam ◽  
Radiation Enhanced Diffusion ◽  
Simultaneous Irradiation ◽  
Radiation Induced ◽  
Red Radiation

ABSTRACTRadiation-induced segregation (RIS) in Ni-12.7% Si and Cu-1% Au alloys was studied using Rutherford backscattering spectroscopy during He and Ne irradiation at elevated temperatures. During single ion-beam irradiation with 1.5 MeV He, strong RIS of Si toward the surface was observed in Ni-12.7% Si. Simultaneous irradiation with 400 keV Ne and 1.5 MeV He almost completely suppressed the Si segregation, even when the calculated damage production rate by Ne was only a few percent of that by He ions. A similar effect of dual-beam irradiation was observed in the Cu-1% Au alloy, i.e., the rate of near surface Au depletion was strongly reduced under simultaneous irradiation. The present result shows that dual-beam irradiation can be applied to control RIS and RED (Radiation Enhanced Diffusion) during ion beam processing.

Ostwald Ripening of {113} Defects Precursors and Transient Enhanced Diffusion

1999 ◽  
Vol 568 ◽  
Author(s):  
Giovanni Manninoo ◽  
Nicholas E.B. Cowem ◽  
Peter A. Stolk ◽  
Fred Roozeboom ◽  
Hendrik G.A. Huizing ◽  
...  
Keyword(s):  
Point Defects ◽  
Ostwald Ripening ◽  
Ion Beam ◽  
Extended Defects ◽  
Defect Band ◽  
Enhanced Diffusion ◽  
Dissociation Energies ◽  
Marker Layer ◽  
High Supersaturation ◽  
Very High

ABSTRACTThe ripening of ion-beam generated point defects into extended defects has been investigated in detail. The interstitial supersaturation has been extracted from boron marker-layer diffusion after annealing under non-equilibrium defect conditions. We measured a very high initial supersaturation followed by a decrease over many orders of magnitude with a characteristic “plateau” related to the presence of {113} defects. A continuum inverse model has been used to properly describe the ripening of point defects into clusters and their evolution in the presence of a remote sink, e.g. the surface. It evidences that a nonconservative Ostwald ripening process takes place inside the defect band during the annealing and sustains the interstitial supersaturation. The model reveals moreover an oscillatory behaviour of dissociation energies of the nanometer-sized defects which are responsible for the initial high supersaturation. These defects are believed to be {113} precursors.

Atomic Transport in Irradiated Solids

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 Enhanced Diffusion ◽  
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.

The Effect of Microstructure on Tensile Behaviour of X80 Microalloyed Steel

2012 ◽  
Author(s):  
Katherine Jonsson ◽  
Douglas G. Ivey ◽  
Hani Henein ◽  
Shahrooz Nafisi ◽  
Laurie Collins ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Treatment ◽  
Work Hardening ◽  
Elevated Temperatures ◽  
Ion Beam ◽  
Hold Time ◽  
Tensile Behaviour ◽  
Microstructural Development ◽  
Line Pipe ◽  
Effect Of Microstructure

A high degree of work hardening is desirable for steels to be employed in strain-based pipeline designs. In an effort to enhance work hardening characteristics, this study was conducted to determine the effect of thermal treatment on microstructural development and the subsequent relationship between microstructure and tensile behaviour of high strength microalloyed line pipe steel. A series of thermal schedules was applied to X80 steel samples using a Gleeble thermo-mechanical simulator in order to generate a variety of microstructures. The microstructures were quantified by calculating the phase fraction of individual phases using scanning electron microscopy (SEM). A focused ion beam (FIB) instrument was used to prepare electron transparent samples of specific grains that were characterized using transmission electron microscopy (TEM). The X80 microstructures were composed mostly of bainitic and ferritic grains with isolated pockets of martensite and M-A islands due to local carbon segregation. The effect of thermal treatment on microstructural evolution was determined based on varying the interrupt temperature, re-heat temperature and hold time at elevated temperatures. The overall effect of microstructure on the mechanical properties was evaluated, with a particular focus on hardness values and the shape of the stress-strain curves. The effect of thermal history and microstructure development on the work hardening characteristics was also determined.

scholarly journals Analysis of Experiments in Helium Microbeam Mixing

1991 ◽  
Vol 235 ◽  
Author(s):  
John B. Davis ◽  
R. E. Benenson ◽  
David Peak
Keyword(s):  
Dose Rate ◽  
Ion Beam ◽  
Liquid Nitrogen Temperature ◽  
Enhanced Diffusion ◽  
Interface Width ◽  
Interface Growth ◽  
Radiation Enhanced Diffusion ◽  
Order Of Magnitude ◽  
Constant Dose ◽  
Diffusion Of Vacancies

ABSTRACTWe have continued to investigate ion-beam mixing in bilay-er targets irradiated by 2-MeV He+ microbeams at room temperature. Although we have previously reported a linear dependence of interface width on dose for Cu/Al targets 1, more extensive results have not supported this conclusion, within statistical uncertainty, it appears that the interface width in Cu/Al (1) is proportional to the square root of dose, at constant dose rate, (2) is larger in Al than in Cu, for the same dose, (3) is proportional to the 1/4 power of dose rate, and (4) is absent at liquid nitrogen temperature. Calculations of the expected interface growth rate from a radiation-enhanced diffusion model have provided order-of-magnitude agreement with observed rates. Additionally, intermixing of Cu and Al outside the damaged area may indicate significant transverse diffusion of vacancies.

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