The Effect of PostProcessing on the Ductility and Strength of Ti-6Al-4V Lattice Materials

Additively manufactured Ti-6Al-4V lattices have found important applications but their mechanical properties remain insufficient, compared with light alloys of similar densities. This study investigates the influence of chemical etching, hot isostatic pressing (HIP) and beta-annealing on the ductility and strength of selective electron beam melted Ti-6Al-4V lattices. We show that applying beta-annealing substantially increased the ductility of Ti-6Al-4V cubic lattices from 8.76% to 32.88% and strength from 194.56 to 321.98 MPa, due to the improved microstructure, which eliminated premature fracture of lattice struts and allowed for significant lattice densification. In contrast, although HIP closed strut internal porosity, it only marginally improved the lattice ductility and strength, much less comparable to beta-annealing. Chemical etching worsened the lattice mechanical properties, attributed to the extra dents left after particle removal. Stress fluctuation was common in the stress-strain curve for as-printed, chemically etched and HIP-processed lattices but absent for beta-annealed lattices, which exhibited smooth and stable stress-strain curves.