Abstract
? 2022 Elsevier B.V.The microstructural evolution and its consequence on the room and elevated temperature (500 °C) tensile properties of the Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti6242S) alloy fabricated via the laser powder bed fusion were investigated after the following heat treatments: solution treatment followed by aging (STA), super-transus heat treatment, and water quenching (WQ) after annealing at a sub-transus temperature (885, 925, 954, and 982 °C) in the (α + β) regime. The super-transus heat treatment results in the removal of columnar prior β grains and formation of equiaxed grains that consist of α colonies. The WQ triggers the formation of a bimodal microstructure of α and α′ phases, and the volume fraction of α′ phase increases with increasing the WQ temperature. The STA process leads to a high yield strength (σy: ~658 MPa) and an elongation to fracture (εf: ~14.8%) when tested at 500 °C. The super-transus heat treatment results in a lower yield strength at both room and elevated temperatures due to coarsening of the α laths. The WQ process allows for the tailoring of the tensile property in a broad window, and the yield strength increased with increasing WQ temperatures. Particularly, the 885 and 925-WQ samples showed a remarkably enhanced strain hardening behavior during tensile tests. The 925-WQ samples exhibited a high σy of ~706 MPa and an εf of ~11.0% at elevated temperature. The samples that underwent STA processing and 925-WQ showed a higher σy while maintaining a decent ductility relative to the conventionally fabricated counterparts at 500 °C, indicating the potential elevated temperature applications for the Ti6242S alloy fabricated via laser powder bed fusion coupled with heat treatment.
NSTL
Elsevier