(5) Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17)

(5) Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) alloy
Ti-5Al-2Sn-2Zr-4Cr-4Mo alloy (occasionally referred to as “Ti-
17” alloy) was developed in the USA in the 1970s as an alloy having
high strength and excellent fracture toughness. Its heat resistant
temperature is approximately 350˚C. In commercial aircraft engines,
the fan and shaft are built as one piece to reduce engine weight. The
yield strength and tensile strength at room temperature are about
1,150 MPa and about 1,250 MPa respectively, higher than those of
Ti-6Al-4V alloy by about 200 MPa. The alloy also exhibits excellent
crack propagation characteristics, and is appropriate for damage
tolerance design. The major relevant standard is AMS 4955. The
yield strength of the STA (Solution Treatment and Aging) material
is 1,055-1,193 MPa, tensile strength is 1,124-1,265 MPa, and elongation
is 5% or higher at room temperature.3)