Investigation of the anisotropic behaviour of laser heat treated aluminium blanks

The continuous research for progressively lighter components moves the attention on the massive adoption of Al alloys. The achievement of such an ambitious goal passes through the definition of innovative manufacturing methodologies able to overcome some of the most hindering limitation of Al alloys, i.e. their poor formability at room temperature. A viable approach is based on the modification of the blank properties through a local heat treatment (to achieve an optimized spatial distribution of ductility/strength), so that the subsequent forming operation can be carried out at room temperature. The implementation of such approach relies on finite element simulations, where the use of a proper constitutive material model plays a fundamental role. In the present work an innovative methodology, already proposed by the authors in a previous research, is again adopted to enrich the characterization of a strain-hardenable Al alloy (AA5754), initially purchased in a pre-strained condition (H32), and locally annealed by means of a laser treatment: in particular, Thanks to the adoption of the DIC, the investigation of the anisotropy showed a strict correlation between the value of the Lankford parameter and the material condition reached at the end of the local treatment. The experimental data were fitted by a sigmoidal function and implemented in a modified Hill plasticity model for the simulation of the tensile test of a locally treated dogbone specimen, showing a good accordance with the experimental results.