ABSTRACT
Unalloyed titanium is non-heat-treatable so that very few fasteners are made of "pure" titanium. There are numerous titanium alloys which are however proprietary developments. Through research a few have surfaced as being the most suitable for threaded fastener manufacture. The workhorse here is the alloy Ti-6A1-4V. Fasteners made from this material have minimum tensile strength of 135 ksi (930 MPa), 125 ksi (860 MPa) yield strength at 0.2% offset, 96 ksi (660 MPa) shear strength, 10% elongation, and a hardness of Rockwell C 30/36. Ti-4A1-4Mn alloy has good creep resistance, stability, and forges well. The relevant strength properties are similar to those of Ti-6A1-4V but with a slightly smaller ductility. Ti-IA1-8V-5Fe alloy delivers a tensile strength of about 200 ksi (1380 MPa). Because of the high strength-to-weight ratio, fasteners of this alloy produce the same holding power as steel fasteners of the same weight and a tensile strength of 350 ksi (2400 MPa). Two other alloys sometimes used in fastener manufacture are Ti-6AI-12Zr and Ti-6AI-6V-2Sn.
