Electron-irradiation induced creep rates in amorphous alloys, a-${\mathrm{SiO}}_2, {\mathrm{Fe}}_{79}{\mathrm{B}}_{16}{\mathrm{Si}}_5, {\mathrm{Cu}}_{60}{\mathrm{Ta}}_{40}$, and ${\mathrm{Cu}}_{50}{\mathrm{Ti}}_{50}$, were measured at room temperature using a miniaturized beam-bending apparatus within a transmission electron microscope operated at 200 keV. The creep rates of these amorphous samples increased nearly linearly with both e-beam current density and applied stress, while a reference crystalline (c-)${\mathrm{SiO}}_2$ sample failed to creep under the same conditions. The irradiation-induced creep compliance of a-${\mathrm{SiO}}_2$ was $\sim 15$ times larger than that of ${\mathrm{Fe}}_{79}{\mathrm{B}}_{16}{\mathrm{Si}}_5$ and over 1,000 times larger than that of the two Cu alloys. Molecular dynamics computer simulations were employed to simulate electron irradiation induced creep using interatomic potentials representing amorphous ${\mathrm{Cu}}_{75}{\mathrm{Zr}}_{25}, {\mathrm{Ni}}_{85}{\mathrm{P}}_{15}$, and ${\mathrm{SiO}}_2$ as model systems. The irradiation induced creep compliances calculated for ${\mathrm{Cu}}_{75}{\mathrm{Zr}}_{25}$ during 200 keV electron irradiation provided good quantitative agreement with the two Cu-based alloys, but that for a-${\mathrm{SiO}}_2$ was $\sim 180$ times too small. These results indicate that unlike neutron or ion-beam induced creep in a-${\mathrm{SiO}}_2$, creep under electron irradiation is dominated by the effects of ionization, owing largely to the far higher ratio of electronic stopping to nuclear stopping for electrons than for ions.

Close

PrevNext

View figure in article

• Creep
• Radiation damage