Neutron and synchrotron radiation diffraction study of the matrix residual stress evolution with plastic deformation in aluminum alloys and composites

The evolution of the matrix residual stress, RS, with compressive and tensile plastic deformation in aluminum alloys and corresponding composites reinforced by alumina particles (15% in vol.) has been investigated. High and moderate strength aluminum alloys, 2014Al and 6061Al, respectively, have been studied. The RS was determined by neutron and synchrotron radiation diffraction in samples treated to a T6 condition and deformed from 0% to 15% plastic strain. The results show that compressive plastic deformation relaxes the hydrostatic matrix RS of all materials to a minimum at around 2–5% plastic strain. At higher strains the hydrostatic matrix RS increases noticeably in the high strength 2014Al alloy and the corresponding composite but only moderately in the 6061Al alloy and the respective composite. On the other hand, no increase of the RS takes place after a large tensile strain. This difference can be attributed to the higher inhomogeneity of the plastic flow in the high strength matrix materials in compression test.