Energetic e-beam is used in welding, 3D printing and imaging of various materials. It is commonly accepted that e-beam irradiation inside transmission electron microscope has negligible effect on the intrinsic mechanical properties of small-volume metallic materials under in situ investigation. However, small-volume aluminum and aluminum alloy are always covered by a layer of amorphous native oxide shell that is sensitivity to e-beam irradiation. E-beam irradiation may exert a non-negligible influence on small-volume metal-oxide shell “composites” via altering deformation behavior of native oxide shell. However, no research has been performed in this direction.  

 Using Al-4Cu alloy as an example, here we show that high-energy e-beam irradiation can dramatically alter the intrinsic mechanical properties of small-volume aluminum alloy. A transition from single-arm source nucleation (collective dislocation behavior) to interface dislocation nucleation was observed in nanoscale Al-4Cu alloy with the aid of e-beam irradiation, leading to the high strain rate sensitivity in small-volume Al-4Cu alloy. In addition, we found that the combined effect of e-beam enhanced viscous flow of amorphous native oxide shell and the strong confinement of oxide shell on Al resulted in the high deformability in small-volume Al alloy pulled below a critical strain rate.This work was published in Acta Materialia 141 (2017) 183-192. The authors include PhD student Shihao Li, Prof. Weizhong Han and Prof. Zhiwei Shan.
Link: http://www.sciencedirect.com/science/article/pii/S1359645417307516