Neutron diffraction measurement of residual stresses in friction stir processed nanocomposite surface layer

The residual stresses in the friction stir processing (FSP) zones have been quantitatively analyzed using neutron diffraction. A commercial aluminum 6061-T651 alloy rolled plate of 10mm thickness and 140 × 165mm dimension was used as the work material. The nominal chemical composition of the material is Al-1.0Mg-0.6Si-0.28Mn-0.2Cr. Aluminum oxide particles, 200 nm in nominal diameter, were used as the reinforcement. The results show that the maximum tensile stress, which is in the longitudinal direction, is around 100 MPa. The hardness in the stir zone is higher than that in the no particle zone because of the existence of the nano particles. The macro-level residual stresses of the aluminum matrix in the FSP Al-Al₂O₃ nanocomposite zone are tensile in all three directions, with peak values around 100 MPa longitudinally. The hardness profile shows that the hardness in the stir zone of FSP Al-Al₂0₃ nanocomposite is higher than that in the without particles material.