Microstructure and mechanical properties of a newly developed Ti-6Al-2Mo-2Sn-2Zr-2Cr-2V alloy fabricated by laser directed energy deposition

Abstract

With the rapid development of aviation industry, the study of novel titanium (Ti) alloy with superior mechanical properties is of great significance. In this paper, a newly developed Ti-6Al-2Mo-2Sn-2Zr-2Cr-2V alloy was fabricated by laser directed energy deposition (L-DED), which exhibits coarse β columnar grains containing the basket-weave structure knitted with α phases and β phases. After solution and aging heat-treatment, the fine secondary α phase precipitates, which leads to the increase in microhardness. The as-deposited sample exhibits the tensile strength of 1025 MPa and the elongation of 6.0%. With solution temperature increasing, the strength increases but the plasticity first increases and then decreases. The fracture mechanism shows a mixed of ductile and brittle fracture. The average impact toughness of as-deposited sample in building direction is 40.9 J cm ^−2 higher than that (23.4 J cm ^−2 ) in direction perpendicular to building direction. After solution and aging heat-treatment, the impact toughness improves significantly.

Keywords

• laser directed energy deposition
• titanium alloy
• solution and aging heat-treatment
• microstructure evolution
• anisotropy