High-pressure solution treating and aging for additive manufactured near-alpha Ti6242 alloy: effects on microstructural properties and high-temperature tensile behaviour

This work investigates the effect of a high-pressure Solution Treating and Aging (STA) heat treatment on the room-temperature (RT) and high-temperature (550 °C) tensile properties of the near-α Ti6242 alloy produced by PBF-LB. The treatment combines solutioning with Hot Isostatic Pressing (HIP) at 1000 bar, followed by argon quenching and aging. High-pressure heat-treatment parameters were first optimized by studying two α+β solution temperatures (960 and 990 °C), corresponding to primary-α fractions of 25 % and 50 %. All samples were aged at 600 °C for 4 or 8 hours to promote a bilamellar microstructure. The condition solutioned at 960 °C and aged for 8 hours (HIP960_8) was selected for mechanical testing. In the second phase, HIP960_8 was compared with a standard STA treatment without HIP, using water quenching and identical thermal parameters (STA960_8), to evaluate the effect of cooling rate. Both were also compared with a β-solution STA treatment with pressurized nitrogen cooling (HT1040_8) designed to produce a fully lamellar structure. Atom Probe Tomography revealed Ti 3 Al precipitation in STA960_8, leading to higher YS and UTS than HIP960_8 at RT (+8 % on YS, +11 % on UTS) and 550 °C (+7 % on YS, +8 % on UTS). In contrast, HIP960_8 provided an excellent strength–ductility balance, with elongation increased by 40 % at RT and 22 % at 550 °C due to its reduced defect content. No STA condition formed silicides because of the low Si content, which contributed instead through solid-solution strengthening, particularly in HT1040_8. Tests at 550 °C confirmed that the bilamellar structure of HIP960_8 offers benefits comparable to solid-solution strengthening in HT1040_8.