PSI - Issue 75

Arthur THIBAULT et al. / Procedia Structural Integrity 75 (2025) 509–518 Arthur THIBAULT / Structural Integrity Procedia (2025)

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During this measurement campaign, micro-tensile tests instrumented with Stereo Digital Image Correlation (Stereo DIC) at the local scale were performed with the aim of evaluating the local elasto-plastic constitutive laws and demonstrating differences in mechanical properties between the fusion zone (FZ) and the base metal (BM). 2. Evaluation of local behavior laws 1.1. Importance of taking into account local behaviours Prior to performing the micro-tensile tests, preliminary studies were conducted in order to validate the hypothesis that the cracks observed in the welded zones are indeed due to differences in local mechanical properties. The first reason to focus on weld behaviour is the use of a different aluminium grade for the filler metal, namely aluminium 4043, used for reasons of weldability. A metallographic study revealed significant microstructural gradient between the base metal (BM) and the weld bead. After the preparation of the samples, the microstructure was revealed by chemical etching with Keller's reagent (2.5% HNO3, 1.5% HCl, 1% HF, 95% H2O). For the base metal, a microstructure is observed comprising a saturated solid solution with nanometric precipitates of and 2 precipitates. In the weld bead, however, a much finer dendritic microstructure is observed, which forms during cooling after welding (Fig. 2a and 2b). a

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Mg2Si precipitates

Saturated Solid Solution

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Fig. 2. microstructure of the base material (a), the weld bead (b) and micro hardness filiation (c)