High strength WE43 microlattice structures additively manufactured by laser powder bed fusion

WE43 is a high strength, high creep resistant Mg-alloy containing Y, Nd, and Zr, and has potential for many lightweight structural applications in the automotive, aerospace, and biomedical industries. Additive manufacturing technology such as laser powder bed fusion (LPBF) brings an opportunity to produce complex geometries such as lattice structures. In this study, fabrication, compressive behavior, and fracture modes of 24 different microlattice structures were investigated by varying unit cell type, strut diameter, and number of unit cells. These complex lattice structures were produced by LPBF using the parameter set: laser power = 200 W, scan speed = 1100 mm/sec, slice thickness = 0.04 mm, which was optimized in our previous study to build fully dense (> 99 %) WE43 alloy. Overall, the lattice structures exhibited oscillations in stress, showing many local maxima and minima, with a global maximum in stress at or near 5 % strain. The highest compressive strength, and the corresponding specific strength found in this study were 71.48 MPa and 38.85 MPa·g⁻¹·cm³, respectively, from the cubic fluorite lattice structure with a strut diameter of 0.75 mm and an unit cell number of 10. During compression testing, two different failure modes were observed: 45° shear fracture and crushing. Due to the inherent low ductility of WE43, brittle crushing was predominant after elastic yielding, which resulted in similar strength-density relationships for each lattice type along with similar failure modes.