A comparative study on dynamic deformation and ballistic impact response of Ti-4Al-2.5V-1.5Fe-0.25O and Ti-6Al-4V alloys

Titanium alloys are most suitable for lightweight armour applications due to their superior strength to weight ratio, and alpha+(3 +(3 Ti alloy Ti-6Al-4V is widely used in armour applications. One of the critical factors limiting the widespread use of Ti alloys in armour application is their high cost. Recently, Allegheny Technologies Incorporated introduced ATI-425 (R) (R) Ti alloy with the chemical composition of Ti-4Al-2.5V-1.5Fe-0.25O as a low-cost alternative to Ti-6Al-4V. Though ATI-425 Ti alloy is primarily intended for armour applications, only limited ballistic results are available in the open literature. In the present work, we compare the quasi-static, dynamic deformation, ballistic impact response and post-deformation microstructure of a low-cost alpha+(3 +(3 Ti alloy ATI-425 with that of Ti-6Al-4V alloy. Analysis of the results showed that both alloys showed similar yield strength values during quasi-static tension and compression tests, while ATI-425 Ti alloy showed higher tensile ductility, CharpyV notch impact energy and dynamic flow stress than Ti-6Al-4V. The ATI-425 Ti alloy also exhibited slightly better ballistic performance measured in terms of V 50 ballistic limit velocity. Detailed microstructural analysis on - - quasi-static and dynamic compression-tested samples showed mainly {1012} tensile twins, whereas {1012} and - {1121} tensile twins are observed in ballistic-tested samples of both the alloys. Activation of deformation twinning in ATI-425 Ti alloy with higher oxygen is attributed to lower Al content which enhances the twinning activity. Adiabatic shear band (ASB)-induced plugging mechanism is ascertained as the perforation mode in both alloys during the ballistic impact. Analysis of propensity to ASB formation indicated that Ti-6Al-4V has a slightly better resistance to ASB formation than ATI-425 Ti alloy. The improved ballistic performance of ATI-425 Ti alloy in comparison to Ti-6Al-4V is attributed to the higher dynamic flow stress, Charpy-V notch impact energy absorption, and moderate resistance to adiabatic shear band formation.