Deformation behaviour in bulk nanocrystalline-ultrafine aluminum: in situ evidence of plastic strain recovery

The plastic deformation behavior of bulk nanocrystalline-ultrafine Al was investigated under in situ compressive loading using high-energy synchrotron X-ray diffraction. After one loading–unloading cycle, to 2% strain, we find reversible peak broadening within the nanocrystalline grain volume and tensile residual stress (80 MPa) within the ultrafine grain volume. Upon unloading, we detect recovery of 12% of the plastic strain, and this recovery increases up to 28% at even higher applied deformations to 4%.