FRICTION STIR ADDITIVE MANUFACTURING OF TITANIUM ALLOYS FOR HIGH PERFORMANCE MILITARY APPLICATIONS

Friction stir additive manufacturing (FSAM) will be utilized for repair, fabrication and processing of Titanium components and sub-assemblies for high performance military applications. The innovation will address the issue of part distortion resulting from high residual stresses imposed during traditional fusion welding based additive manufacturing techniques. In addition to enhancing dimensional stability, the proposed innovation will lead to high performance parts with properties equivalent to wrought products. This will address the second issue associated with fusion additive manufacturing techniques, which is production of inferior parts because of the resulting cast microstructure. Furthermore, the technology will lead to high build rates, approximately an order or two orders of magnitude higher than fusion additive manufacturing technologies. All the FSAM work will be done on the army preferred a+ Ti-6Al-4V alloy and other high strength near/metastable , Ti-6Al-2Sn-4Zr-6Mo, Ti185 alloys that are promising for armament systems. For built-up structures using FSAM, two different approaches will be adopted. In the first approach, the above mentioned a+ and near alloy sheets will be joined using a non-consumable tool to give near-net 3D shape. The second approach will use a laser-FSAM hybrid process to create flexibility in the form of heat input, reduce