Thermomechanical Modelling of Laser Powder Bed Fusion in Bimetallic Systems: Residual Stress Analysis and Influence of Scan Strategy

Laser powder bed fusion (L-PBF) offers advanced capabilities for producing multi-material components with intricate geometries. Nonetheless, the parts built by this promising additive manufacturing technique face significant challenges due to thermomechanical stresses generated by the building process at the interface between dissimilar materials. Indeed, mismatched properties and steep thermal gradients can induce high residual stresses and plastic strains, potentially leading to the failure of the fabricated parts. A microscale thermomechanical finite element model of the L-PBF process in the case of AlSi10Mg/CuCrZr bimetallic systems was developed to predict stress and strain distributions within an interfacial elementary volume composed of a few laser tracks on several built layers. Laser energy deposition was modeled as a surface Gaussian heat source and latent heat effects during phase transitions were incorporated. Both powder-to-bulk transitions and layer depositions were accounted for in the simulations to closely mimic the L-PBF process. Waiting steps during powder and layer transitions were also implemented to better capture thermal evolution and allow the study of residual stresses and strains. Various scan strategies were investigated to assess their impact on the generation of residual stresses and strains, with a particular emphasis on the interfacial regions, providing insights on optimizing process parameters in case of bimaterials.