Microstructures and mechanical behavior of a near α titanium alloy prepared by TiH2-based powder metallurgy

Abstract

This study investigated microstructures and mechanical behavior of a powder metallurgy (PM) Ti–3Al–2Zr–2Mo marine titanium alloy. This PM alloy was prepared by a fast sintering and immediately followed hot extrusion of TiH2-based powder compact. Most of the β-phase strips in as-extruded sample were found to become discontinuous via a dehydrogenation reaction of β (H) → α + β + H2 during vacuum annealing. Such annealing rendered this alloy an excellent ultimate tensile strength up to 1080 MPa and a superior elongation to fracture of 14.0%. Further, a common annealing of 920 °C/1 h/AC brought about a lamellar microstructure consisting of coarsened α laths and β-transformed structures. Consequently, the ultimate tensile strength decreased slightly, the elongation decreased to 9.50%. It was noteworthy that the present PM alloy samples exhibited a satisfying combination of superior tensile strength and excellent ductility, which was ascribed to the reasonable oxygen solution and particular lamellar microstructures containing high content of β-transformed structures. Work hardening behavior of the present alloy was investigated, in order to explain the reason for the highly promising mechanical properties.