Manipulating stacking fault energy and coherent L1 2 precipitation for suppressing crack initiation in laser additive manufacturing high-entropy alloys

Laser additive manufacturing (LAM) is widely used to produce high-performance and complex parts due to its high energy density and near-net-shaped capability. However, LAM-produced components are often compromised by cracks caused by severe residual stresses. In this study, cracking was suppressed and mechanical properties were enhanced by tailoring the alloy composition to manipulate the stacking fault energy (SFE) and discontinuous precipitation of coherent L12 phase at grain boundaries. Using a high-entropy alloying strategy based on cluster-plus-glue-atom model, a series of [Al-Co4 + xNi8-x]Cr2Ti high-entropy alloys (HEAs) was developed. Replacing Ni with Co effectively lowered SFE and reduced the size of the ordered L12 phase, which together dissipated thermal stress during laser directed energy deposition (LDED). Among the designed alloys, the [Al-Co8Ni4]Cr2Ti composition achieved a crack-free LAM build, exhibiting the lowest SFE and the smallest L12 precipitate. Lowering the SFE increases dislocation activity and relieves residual stress, thereby reducing crack initiation, while discontinuous precipitation of L12 phase at grain boundaries inhibits crack propagation. This work offers a new strategy for designing crack-resistant HEAs with a high-volume fraction of coherent L12 precipitates for additive manufacturing applications.