Influence of alloying elements on grain-growth in Zr(Fe) and Cu(Fe) thin-films under in situ ion-irradiation

Thin-films of Zr(Fe) and Cu(Fe) were ion-irradiated in situ in a transmission electron microscope to study the influence of alloying elements on grain-growth. These two systems are different in that Zr–Fe has a negative heat of mixing and Cu–Fe a positive heat of mixing. Irradiations conducted at temperatures of 20–573 K showed precipitation in Zr(Fe) but not in Cu(Fe). The grain sizes increased monotonically with fluence and in both cases the pure metal exhibited more grain-growth than the alloy. A more drastic reduction of grain-growth rate was observed in Zr(Fe) (where precipitate drag occurred) than in Cu–Fe (where only solute drag was available). Zr(Fe) samples were also subjected to 1 MeV electron irradiation but no grain-growth was observed. The results are discussed in terms of the mechanisms of grain-growth under irradiation.