Crystal plasticity in fusion zone of a hybrid laser welded Al alloys joint: From nanoscale to macroscale

Highlights: • Nano/microplasticity in fusion zone from our experiments can be used to predict the macro-plasticity of the joint. • The nano/microplasticity in fusion zone depends significantly on sample's size. • Nano/microplasticity is affected by orientation whose influence deceases in larger samples. • Numerical models are constructed and used to assess the size and orientation effect. In this paper, we propose a novel approach to predict the plasticity of hybrid laser welded Al alloys joints based on the microplasticity obtained from the micropillar compression test. The micropillar test was performed on the single-crystal pillar with three orientations and various diameters (400 nm to 6.8 μm). It was found that independent of orientation, the yield strength of the pillar increased with the decrease of diameter below a critical length (3.3 μm). A numerical model was successfully built and used to explain the size effect on the pillar's strength. Crystalline orientation did affect the yield strength, the orientation having higher Schmid's factor showing lower yield strength, but the effect was reduced with the enlarged diameter. The macroscale yield strength achieved from crystal plasticity finite element simulation showed was found to have a good agreement with that from the experiment. The results here shed new insights both on the application of the micropillar study of alloys, and on prediction of strength in welded Al alloys joint.