Promoting direct and ultrafast precipitation of the α phase in the metastable Ti-10V-6Cu alloy

Abstract

Direct aging of water-quenched metastable β-titanium alloys usually follows the sequence: rapid growth of ωiso and then slow transformation into α. To inhibit ωiso growth and promote α nucleation, 6% pre-deformation was introduced in Ti-10V-6Cu alloy before 500°C/60s aging. An ultrafast α-formation and a few α-free kink-bands are observed, indicating the alteration of the precipitation sequence. For α-nucleation without ωiso as the sites, it shows that O' nanodomains induced by stress accumulation around slip bands mediate the ultrafast nucleation of hcp-α structure, while dislocation pipe diffusion accelerates the necessary phase separation. This provides new insights into regulating precipitation kinetics of age-hardenable β-titanium alloys.

Keywords

• Titanium alloys
• precipitation sequence
• nucleation
• HAADF-STEM
• atomic structure