RESIDUAL STRESSES IN AS-CAST BILLETS: NEUTRON DIFFRACTION MEASUREMENT AND THERMOMECHANICAL MODELING

Stress relief treatment is often required prior to sawing aluminum DC cast products in order to prevent crack formation and significant safety concerns due to the presence of high residual stresses generated during casting. Numerical models have been developed to compute these residual stresses and yet have only been validated against measured surface distortions. In the present contribution, the variation in residual strains and stresses have been measured using neutron diffraction in two AA6063 grainrefined cylindrical billet sections cast at two casting speeds. The measured residual stresses compare favorably with the numerical model, in particular the depth at which the axial and hoop stresses change sign. Such results provide insight into the development of residual stresses within castings and show that the stored elastic energy varies linearly with the casting speed, at least within the range of speeds that correspond to production conditions.