Energy density–defect–property relationships in LPBF of ferrous shape memory alloy

Laser powder bed fusion (LPBF) of FeMnAlNi shape memory alloys offers a promising route for manufacturing functional components; however, the relationships between processing parameters, defect formation, and resulting properties remain insufficiently understood. This study investigates the influence of laser power (150–250 W) and scanning speed (500–1000 mm/s), corresponding to volumetric energy densities (Ev) of 50–166.67 J/mm³, on densification, thermal behavior, mechanical performance, and phase transformation characteristics. Results show that Ev governs melt pool stability and defect formation, with low Ev leading to lack-of-fusion defects and high Ev promoting keyhole porosity. An optimal processing window (≈ 72–106 J/mm³) achieved relative densities up to 99.33% with minimized defects. Mechanical performance strongly correlated with densification, with yield strength up to ~ 560 MPa, ultimate tensile strength up to ~ 1480 MPa, and hardness reaching ~ 448 HV. Cyclic compression demonstrated recoverable strain within a defined stress range. Magnetization results indicate that processing conditions influence phase transformation behavior, with improved transformation response observed within the optimal processing window. This work establishes a processing–defect–property relationship for LPBF-fabricated Fe–Mn–Al–Ni alloys and provides guidance for achieving high-density components with improved mechanical and functional performance.