Weight reduction is an important criterion in selection of armour materials used in different defence applications. Among the various novel materials that are being studied for lightweight armour applications, Ti alloys are potential candidates due to their high strength to weight ratio, corrosion resistance and good ballistic performance. Among Ti alloys, the α+β Ti alloy, Ti-6Al-4V is the most commonly used alloy for various armour applications as it offers about 30% weight reduction over traditionally used rolled homogenous armour steels . Recently, a α+β titanium alloy with a composition of Ti-4Al-2.5V-1.5Fe-0.25O (ATI-425®) was developed by Allegheny Technologies Incorporated, in which some parts of the high cost β-stabilizing element V is replaced with low cost Fe. Due to its lower cost, processing advantages and promising ballistic results, Ti-4Al-2.5V-1.5Fe is a potential candidate for future armour applications.
There are very limited studies on microstructure and mechanical properties correlations of the newly developed α+β titanium alloy Ti alloy, Ti-4Al-2.5V-1.5Fe. It is well known that thermo-mechanical processing strongly influences microstructure and mechanical properties in titanium alloys. It is therefore important to optimize its thermo-mechanical processing route to achieve the desirable final microstructure, mechanical properties and the ballistic performance. In this work, we will study the thermo-mechanical behaviour of this alloy at temperatures above and below β-transus temperatures with an aim to obtain suitable processing parameters for β and α+β processing. Further, the effect of post processing heat treatment on microstructures and mechanical properties (such as tensile behavior and Charpy-V notch impact toughness) will be studied. We will evaluate the ballistic performance of ATI-425 Ti alloy with different microstructures (equi-axed, lamellar and bimodal) and results will be compared with the results of Ti-6Al-4V. The introduction of any new material to armour application requires understanding of its plastic flow response at higher strain rates. In view of this, we propose to study the deformation behaviour of Ti-4Al-2.5V-1.5Fe alloy with different microstructures (equi-axed, lamellar and bimodal) at wide range of strain rates ranging from 10-3/s to 103/s. Comprehensive microstructural analysis will be used to understand the deformation response of the alloy as a function of strain rate in terms of operating deformation micro-mechanisms.