On the Nature of Radiation Damage in Metals

Abstract

The nature of the permanent damage retained in metals from irradiation has been investigated in somewhat greater detail than has been done in the past. The usual assumption has been that the damage in all metals consists chiefly of interstitial-vacancy pairs. The model presented in this paper reduces to this picture for the light elements but introduces a new concept in the case of damage in the heavy metals, called a displacement spike. Calculations are made from which one can estimate the relationship between the density of interstitial-vacancy pairs and the temperature of the associated thermal spike. An assumption regarding the extent to which interstitial-vacancy pairs persist throughout the duration of the thermal spike has been made, based upon these calculations. The number of interstitial-vacancy pairs predicted in the heavy elements is considerably smaller than that predicted by the former model. A mechanism is proposed by which small dislocation loops can be produced in the heavier metals by irradiation. This article is based upon studies conducted for the U. S. Atomic Energy Commission under Contract AT-11–1-GEN-8.

Molecular dynamics simulations of point defect production in cementite and Cr23C6 inclusions in α-iron: Effects of recoil energy and temperature

“…31 For the cells with inclusions there is a pile-up of defects at a radial distance slightly lower than the initial radius of the inclusion. This effect is of course not seen for the pure cells where there is no interface.…”

Amorphization of crystalline Si due to heavy and light ion irradiation

“…Under situations where the mean free path of the displacing collisions approaches the interatomic spacing, small highly perturbed regions can be formed within which the mean kinetic energy of the target atoms may be increased by several eV-this is the displacement spike. 1 As the kinetic energy deposited by the spike begins to dissipate, localized melting in the spike region may occur. This is known as the thermal spike.…”

Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu

“…Of particular note, the combination of the methods for characterizing radiation damage effects from the EXAFS measurements demonstrates that Debye-Waller enhancements of the Ga-Pu nearest-neighbor pairs and the estimated crystalline fraction of the material indicate that the Ga environment is actually more ordered at annealing temperatures below 50 K than above, suggesting that Ga attempts to form locally ordered structures during the initial damage event, on the order of 10 −11 s when the material is essentially melted by the deposited energy, 69 and this order is quenched into the material, and may be responsible for most of the residual resistivity observed in other experiments. Above 50 K, the Ga diffuses 19 into the main damaged Pu matrix and the Ga local environment takes on a more average structure.…”