摘要
This study investigates the microstructure and tensile properties of Al3.6Co27.2Cr19Fe18Ni26Ti5.5Zr0.01Si0.3 high entropy alloy (LPBF-HEA) with varying niobium carbide (NbC) additions processed through laser powder bed fusion (LPBF). In as-LPBF state, NbC acts as heterogeneous nucleation site, resulting in 74% grain size and 68.5% cell size reduction as NbC content increased from 0 wt% to 5 wt%. Two heat treatment were applied: solution heat treatment followed by aging and direct aging. The solution treatment at supersolvus temperature minimizes micro-segregation, while the direct aging with subsolvus temperature preserves the cell structure and promotes a hierarchical microstructure, evidenced by the formation of L12 and L21 precipitates. The grain and cell size refinement, and carbide dispersion strengthening resulted from carbide addition contribute to outstanding strength improvement, yielding a 285 MPa yield strength increase in as-built samples with 5 wt% NbC. L12 precipitation provides a strong strengthening contribution of 500 MPa in heat-treated conditions, while the cell structure provides further strengthening effect in as-built and direct-aged samples. However, the aggregated NbC and the brittle L21 precipitates along grain and cell boundaries cause the ductility loss. This study highlights the flexibility of microstructure design in LPBF processed HEAs through heat treatment and carbide addition. © 2026 Elsevier B.V.