Anisotropic Mechanical Properties of Al-Mg-Sc-Zr Alloy Fabricated by Selective Laser Melting

This work investigates the microstructure, defects, static and fatigue performance of Al-Mg-Sc-Zr alloy built using selective laser melting (SLM) in 0° and 90° directions. The results show that the alloy has a bimodal structure with coarse columnar grains (CG) and fine equiaxed grains (FG) in XZ plane and EGs in XY plane. Benefiting from the grain refinement and precipitation strengthening, the yield strength (YS) in both directions exceeds 500 MPa, while the lack of fusion (LoF) defects reduce the ductility of 90° specimens. The anisotropy of K IC is not apparent, while obvious fatigue crack growth (FCG) properties can be observed due to the directional LoFs and anisotropic microstructure. The LoFs lead to faster FCGR for 0° CT specimens in near-threshold regime, while the FCGR in 0° CT specimens is lower in steady state regime due to transgranular cracking. For the fatigue properties, although a large scale of scatter can be observed, the 0° specimens have a much longer fatigue life compared to 90° specimens. The LoFs are the main factor that contribute to the anisotropic fatigue properties as they are typically perpendicular to the build direction.