Advanced processing techniques for titanium base alloys and its aluminides for space applications

Abstract

Indian Space programs require high specific strength materials with compatibility to various working fluids/environments. Titanium alloys possess these characteristics and hence are materials of choice for various space applications like high pressure gas bottles and upper stage propellant tanks of launch vehicles and satellites. For these applications, main contribution is from the workhorse two phase (α+β) Ti-6Al-4V alloy, which is used in annealed as well as STA (solution treated and aged) conditions. Further, application at extremely low temperature of 20K requires a special grade single phase (α) Ti-alloy, namely Ti-5Al2.5Sn-ELI (extra Low Interstitial). For these two alloys, processing techniques required for fabrication of various components is established through closed-die forging / plate-forming / ring rolling, machining and EB welding. Close control on the processing parameters are mandatory to achieve desired microstructure, mechanical properties and cost effective components. Indigenous development of a new high strength Ti-15-3 (metastable beta) alloy is accomplished, offering advantage of amenability to cold forming and attainment of very high strength through aging. This can lead to processing of lighter, cost effective and near net shape components and thin-sheet-structures.