Mitigating defects at copper-steel interfaces via a lack of fusion-informed power increment strategy in multi-material laser powder bed fusion

Multi-material laser powder bed fusion combines different materials in a single component, enabling enhanced functionalities without additional manufacturing steps. However, joining CuCrZr with 316L is challenging due to property mismatches, often leading to poor interfaces. A novel layer-wise power increment strategy is proposed, starting with low laser power for the initial CuCrZr layer on steel and gradually increasing it for subsequent layers. This approach uses a ring-mode laser to create shallower melt pools, which reduces intermixing but poses a risk of lack of fusion (LoF) defects. A melt pool geometry-based process model using smoothed particle hydrodynamics simulations is developed to predict LoF, optimize power settings, and analyze dynamics not observable experimentally. Experiments show that a saturating exponential power increase reduces LoF up to 24% compared to a linear strategy. Although minimum power is used at the first interface layer, LoF pores occur between layers 3–8 due to rising thermal conductivity in the growing structure. This effect stabilizes near layer 6, making power control in the first five layers critical. The LoF prediction framework proves effective in developing these parameters. Furthermore, the method confines intermixing to one layer (<40μm), preventing copper contamination cracking while maintaining robust fusion.