A longitudinal gradient architecture achieves better tensile properties in Ti6242 alloy

Abstract

Simultaneous increase in strength and ductility is obtained in Ti6242 alloys using a longitudinal gradient structure. Such architecture demonstrates strain hardening regarding the gradient layer's volume fraction (Vf). The maximum strain hardening is produced in the freestanding gradient layer (Vf = 100%). An extra strain hardening evidenced by the increased back stress occurs in gradient samples, which partly accounts for the concurrently improved properties. Additionally, more boundaries of the α/β plates in lamellar structure and increased dislocations in the primary α phase (αp) are responsible for the enhanced strength. In the gradient layer, such microstructural characteristics, including significant thinning of the β plates, the locally disappeared boundaries of αp and transformed β structure (βt), and the reduced property difference between deformed αp and βt, contribute as well on the ductility improvement. This work provides a guideline for manufacturing high-performance Ti alloys via microstructural regulation or gradient architecture.