The Effect of Heat Treatment on the Mechanical and Corrosion Properties of Ti-6Al-4V Alloy Additively Manufactured by Laser Powder Bed Fusion

Titanium alloys are widely used in aerospace and other fields due to their low density, high specific strength, and high corrosion resistance. In order to study the effect of heat-treated microstructure on the mechanical and corrosion properties of Ti-6Al-4V alloy additively manufactured (AM) by laser powder bed fusion (L-PBF), three sets of samples are prepared: as-built state, 650℃/4h stress relief heat treatment, and 800℃/2h annealing heat treatment. A systematic study is carried out by combining microstructure characterization, XRD phase analysis, TEM observation, tensile testing, and electrochemical testing. The results show that the as-printed sample forms a fully α′ martensitic structure due to rapid cooling, exhibiting high strength (ultimate tensile strength of 1260 MPa) but limited plasticity (elongation of 13.06% ) and excellent corrosion resistance (passivation current density of 1.03×10?? A·cm?2). The 650℃/4h heat treatment promoted partial decomposition of the α' phase, resulting in a slight decrease in both tensile strength and total elongation (1141 MPa and 13.51%, respectively), but a significant deterioration in corrosion performance (passivation current density increased to 1.66×10?? A·cm?2). The annealing treatment at 800℃ facilitates the transformation of α' martensite to α/β dual-phase lamellar structure. While reducing tensile strength to 990 MPa, it increases the total elongation to 17.51% and partially restoring the corrosion performance (passivation current density of 1.23×10?? A·cm?2). This study confirms that post-AM heat treatment can simultaneously alter the strength-plasticity balance and corrosion behavior of L-PBF processed Ti-6Al-4V alloy by regulating the degree of martensitic decomposition, thereby achieving overall performance improvement of the alloy.