Coupled effects of topology and Al content on microstructure and mechanical behavior of LPBF-fabricated FeCoNiCrTi0.2Alx porous HEAs via multiscale studies

This study, by combining molecular dynamics simulations, finite element simulations, and laser powder bed fusion (LPBF) experiments, systematically reveals the coupled regulation mechanism of four topological structures (tetrahedral, diamond, octahedral, and dodecahedral) and Al content (x = 0–0.3) on the microstructure, mechanical properties, and fracture behavior of FeCoNiCrTi 0.2 Al x porous high-entropy alloy (HEA). LAMMPS simulations show that the plastic deformation of the alloy is jointly mediated by the slip of 1/6 < 112 > Shockley partial dislocations and the FCC-to-HCP phase transformation. The strength reaches its peak value when the Al content is 0.3, and Al achieves significant strengthening by increasing lattice distortion and reducing stacking fault energy. DEFORM simulations and experiments confirm that the compressive response of porous structures is highly dependent on the topological configuration. Due to the supporting effect of horizontal struts, the tetrahedral structure exhibits the highest compressive strength (reaching 905.54 MPa for FeCoNiCrTi 0.2 Al 0.3 ) and elastic modulus (5019.94 MPa), but a relatively short plastic plateau stage. The diamond structure exhibits the optimal energy absorption capacity (reaching 198.12 MJ/m 3 ) and the longest densification strain (~ 53%) due to the progressive bending of inclined struts. The octahedral and dodecahedral structures show intermediate performance. This study provides a theoretical basis and experimental support for the design and application of lightweight porous HEAs.