Ordered Alloys Reveal Fundamental Mechanisms of Neutron-Damage Production

摘要

Magnetic saturation measurements performed on Ni sub 3 Mn during neutron irradiations are briefly reviewed and critically re-examined. Disordering during thermal-neutron bombardment at 5 exp 0 K uniquely revealed the existence,number and average length of replacement collision sequences. Confirmation of our analysis by others is presented; some refinements are introduced; comparisons with recent molecular-dynamic calculations are drawn; and the (n, gamma ) recoil spectrum in Ni sub 3 Mn is reanalyzed. It is concluded that 112 to 150 replacements occur, within one or two sequences, per (n, gamma ) recoil with an average energy of 492 eV. Similar measurements on Ni sub 3 Mn during fast-neutron bombardment at 5 exp 0 K yielded the total number of replacements per typical 30 keV cascade and demonstrated that very few interstitials were produced at large distances from the cascade by replacement sequences. Recent results on high-resolution TEM measurements of disordered zones in fast-neutron irradiated Cu sub 3 Au are discussed and compared with damage calculations for the accurately measured fast-neutron flux and energy spectrum in CP5 and reveal the spatial characteristics of the deposited energy in individual cascades. Resistivity measurements of Cu sub 3 Au during fast-neutron bombardment at 150 exp 0 C have revealed both the disordering process within cascades and ordering by irradiation-enhanced vacancy diffusion. These experiments provide a means of comparing different neutron energy spectra and studying irradiation-enhanced diffusion in a system amenable to theoretical treatments. (ERA citation 08:021046)