Ion induced disordering and dissolution of Ni3Al precipitates

Abstract

The disordering of homogeneous Ni3Al and decomposed Ni(Al) alloys under irradiation with 300 keV Ni58 ions is studied at room temperature. In order to determine the development of the long-range order parameter, electron diffraction patterns are quantitatively evaluated taking into account dynamical diffraction effects. Although postulated by a recent model based on the thermal spike concept, no finite rest order is observed in the high-dose limit. The disordering rate of Ni3Al precipitates is much higher than that of homogeneous Ni3Al which is explained by the additional chemical dissolution of the particles due to ballistic mixing.

Microstructure, chemistry and mechanical properties of Ni-based superalloy Rene N4 under irradiation at room temperature

“…Irradiation-induced disordering of LRO precipitates is attributed to the creation of vacancies, interstitials and anti-site defects, which can disrupt the chemical and structural ordering of the precipitates [14][15][16][17][18]. However, as diffusion is enhanced, for example, by irradiation or thermal annealing, the disordered atoms tend to return to the equilibrium sites and the annihilation of defects can be promoted [12,19,20].…”

Energetic ion beam induced crystal phase transformation and resulting hardness change in Ni3Al intermetallic compound

“…Much work has been carried out on Ni 3 Al irradiated with energetic electron beams or ion beams [11][12][13][14][15][16], however, these irradiation experiments were mainly carried out on Ni 3 Al thin films and changes in the lattice structure were observed by transmission electron microscopy (TEM). There have been few studies for the effect of energetic ion irradiation for bulk Ni 3 Al.…”

Effect of He on the Order-Disorder Transition in Ni3Al under Irradiation

“…Molecular dynamics and ion irradiation studies indicate that disordering is caused by thermal spikes induced by collision cascades [11][12][13][14][15][16]. Rate theory, on-the-fly kinetic Monte Carlo and ion irradiation experiments indicate that re-ordering is caused by mono-vacancies [2,17,18]. Reordering can only take place at temperatures where mono-vacancies are sufficiently mobile, typically above 750 K. The effect of He on the order-disorder competition has-to the best of our knowledge-not been studied.…”

“…A figure case of such an interplay is the disordering of γ Ni 3 Al phases in X-750-a Ni-based superalloy [2]-under neutron irradiation. From a practical point of view, this interplay is critical to the long-term performance and safety of CANDU reactors, where this alloy is used for garter springs separating pressure tubes from calandria tubes.…”

“…For instance V 2 He Dis (1nn) → V 2 He Ord (1nn) is active if both vacancies of a di-vacancy are in the nearest neighbour of the atom in the wrong sublattice. This restriction limits the choice of configurations to 2 12 Z α and 2 12 Z β for Ni and Al in the wrong sublattices, respectively. Therefore, the Boltzmann factor for the V 2 He is:…”