Effect of post-treatment on lattice structure and properties of additively prepared Ti–6Al–4V alloy

Compressive mechanical properties of lattice structures made of titanium alloy Ti–6Al–4V, obtained using selective laser melting, are studied in three different metal conditions: in as-built SLM state, after chemical-heat treatment by ion nitriding, and after annealing. Specimen relative porosity is 50, 60, 70 and 80%. It is established that ion nitriding of lattice structures leads to formation upon them of antifriction layer surfaces several tens of micrometers thick. It is revealed that nitrogen saturation of surface layers for specimens with a degree of porosity of 50, 60, 70% does not have a significant effect on basic mechanical properties during compression, although it leads to an increase by more than 20% in surface hardness of beam elements. It is established that annealing at 720 °C leads to decomposition of the original martensitic α′-phase and to formation of a two-phase (α + β) structure, and removal of residual stresses.