Residual Stress Measurement with Oscillation Method of an Aluminum Alloy Forged Part with Coarse Grains by Neutron Diffraction

The residual stresses in a forged part made of an aluminum alloy with grain size of approximately 1.0 mm were determined by neutron diffraction where the oscillation method was employed. An optimal range of the oscillation is discussed from the relations between the gauge volume and the number of crystal grain. It is found that the stress measurement could be performed with the oscillation range of ±3 degrees if 1000 grains exist in a gauge volume. The influence of diffraction-plane reveals that adoption of (311) requires smaller oscillation angle than (111), (220) or (200). The hydrostatic tensile stress of about 100 MPa was observed inside the part, which was caused by thermal misfit strains caused during cooling after the heat treatment.