Giant faults in deformed Gum Metal

Abstract

We have experimentally characterized and theoretically described plastic flow localization in Gum Metal, a special titanium alloy with high strength, low Young’s modulus, excellent cold workability and low resistance to shear in certain crystallographic planes. The electron transmission microscopy experiments demonstrate that plastic flow is localized in giant faults – macroscopic planar defects carrying very large plastic strains (thousand percent or more) – in deformed Gum Metal. Also, regions with highly inhomogeneous elastic strains and varying crystal lattice orientation are experimentally observed in the vicinity of giant faults. A theoretical model is suggested describing the generation of giant faults as a process resulting from generation and evolution of nanodisturbances (nanoscopic planar areas of local shear) in Gum Metal. It is shown that giant faults can effectively nucleate and evolve in Gum Metal, and their intersection with grain boundaries produces both elastic strain accumulation and inhomogeneities of crystal lattice orientation. This behavior of giant faults is expected to be essential for excellent cold ductility of high-strength Gum Metal.