Evaluation of Newly Developed Ti-555 High Strength Titanium Fasteners

Titanium alloy 555 (Ti-5Al-5Mo-5V-3Cr-0.5Fe), emerging high strength alloy, is capable of very favorable combination of strength, strength-weight ratio, ductility and toughness that expanded use of titanium in many applications. In the past few years, Alcoa Fastening System (AFS) has successfully launched a series of high-strength titanium fasteners using Ti555 in many aerospace fastener applications, from threaded pins to panel fasteners and blind bolts applications.  For close tolerance threaded pins, Ti555 Aero-Lite fasteners can offer more robust properties with higher strength, ductility and toughness than traditional Ti-6Al-4V pins. It can achieve 180 ksi tensile strength and 108 ksi double shear strength up to 0.5 inch diameter. The newly developed Panel (Mark IV) fastener with high strength Ti555 studs achieved 180 ksi tensile strength and 40% weight reduction when compared to similar A-286 studs.  A new high strength Blind Bolt system using Ti-555 as corebolt is in a late stage of development.  It is configured to generate high joint preloads, high shear strength up to 105 ksi, and large blind side foot prints of 1.5 x the nominal shank diameters.  This paper summarizes the mechanical properties and microstructures and discusses a few aerospace fasteners products developed using Titanium alloy 555 material.