A Comparative Study on the Substructure Evolution and Mechanical Properties of TIMETAL^® 407 and Ti-64

Abstract

Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio. Alpha/beta titanium alloys are used in nearly all sections of the aircraft, including the fuselage, landing gear, and wing. Ti-6Al-4V is the workhorse alloy of the titanium industry, comprising of nearly 60% of total titanium production. TIMETAL® 407, Ti-0.85Al-3.9V-0.25Si-0.25Fe (Ti-407) is an excellent candidate for alloy applications requiring excellent machinability and increased energy absorption. These properties are a result of the alloy’s increased ductility while maintaining moderate levels of strength. In this study, the deformation mechanisms of Ti-407 have been studied at high strain rates using split-Hopkinson bar testing. Utilizing post-mortem characterization, Ti-407 has been shown to deform significantly by ⟨c+a⟩ slip and deformation twinning. The observation of ⟨c+a⟩ slip is in contrast with other studies and will be discussed further.

Deformation and failure behaviour of a titanium alloy Ti-407 with reduced aluminium content: A comparison with Ti-6Al-4V in tension and compression

“…The higher propensity of Ti407 to deform by <c+a> slip has been reported in a recent study [12]. It was suggested that the high degree of strain experienced is likely due to…”

“…Dynamic testing in alpha-beta titanium alloys may activate the <c+a> slip systems and is commonly accompanied by deformation twinning. The crystallographic features and mechanical response associated with the Ti407 alloy are not well P. Li 27/01/2021 5 established and there is little published literature available [3,12]. Therefore, more data is needed to quantitatively assess some of the proposed advantages of Ti407.…”

A low-cost machinability approach to accelerate titanium alloy development

“…The Ti-407 however consistently formed a dense region of mechanical twins just below the machined surface. The mechanical twins provide a mechanism for the material to accommodate more strain before fracture occurs which is an idea put forward by Kloenne et al 45 to explain the improved ductility of Ti-407.…”