Static magnetic field-driven optimization of Ti6Al4V lattice architectures fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) of Ti6Al4V lattice structures is particularly sensitive to unstable melt behaviour, limited heat dissipation, and geometry-dependent defect formation at thin struts and node junctions. Although static magnetic fields (SMF) have been used to regulate solidification in bulk additively manufactured alloys, their influence on defect evolution and mechanical response in architected lattices remains insufficiently understood. In this study, optimized octahedral structure (OOCS) and hybrid reinforced structure (HRS) lattices were fabricated by LPBF under SMF of 0, 0.22, and 0.42 T. Surface morphology, three-dimensional defect distributions, crystallographic features, martensitic substructures, and compressive behaviour were evaluated using surface profilometry, X-ray micro-computed tomography, EBSD, TEM, optical microscopy, and quasi-static compression testing. Increasing the magnetic-field intensity progressively reduced surface roughness and internal defect content. At 0.42 T, the volumetric porosity decreased from 0.79% to 0.55% in the OOCS lattice and from 4.93% to 0.29% in the HRS lattice. The SMF-assisted specimens also exhibited reduced long-range martensitic orientation continuity and more segmented prior-β boundary traces and α′-martensitic features, consistent with altered directional growth and solidification conditions. Correspondingly, the compressive yield strength increased from 60.6 to 120.7 MPa for the OOCS lattice and from 67.8 to 128.3 MPa for the HRS lattice. These results indicate that SMF assistance can improve lattice manufacturability by reducing geometry-dependent defects and stabilizing the subsequent compressive response. The observed trends are consistent with magnetic-field-mediated modification of melt flow and solidification, although direct melt-pool measurements are required for complete mechanistic confirmation.