Structural modifications and electron beam damage in aluminium alloy precipitate θ'–AL₂

Abstract

The –AlCu phase in an Al–4Zn–2Cu–1Mg–0.7Si (wt.%) alloy was investigated by means of scanning transmission electron microscopy. With our specific alloy composition, the phase is often formed with stacking faults on and planes. The stacking faults on planes are often regularly spaced and create a previously unreported superstructure. Structural damage by electron irradiation is observed, even at a low acceleration voltage of 80 kV. The damage is more pronounced in the precipitates with stacking faults, which agrees with theoretical calculations of knock-on scattering cross-sections. These two very different forms of disruptions of the structure are linked to its spacious interstitial sites and the ease at which Cu atoms diffuse into and between them.

Keywords:

• alloys
• precipitation
• structural transitions
• irradiation effects
• transmission electron microscopy

Acknowledgements

The authors would like to thank the Research Council of Norway (RCN) for funding of the FRINATEK project “Fundamental investigations of precipitation in the solid state with focus on Al-based alloys”.

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the project NORTEM [grant number 197405], [grant number 221714] within the programme INFRASTRUCTURE of the RCN. NORTEM was co-funded by the RCN and the project partners NTNU, UiO and SINTEF.