Abstract

The materials examined in this study included three conventional titanium alloys: Timetal[reg sign]21S (Ti-8Mo-1.5Nb-5.7Al-0.4Si), Ti-6242S (Ti-10.6Al-0.8Sn-2.1Zr-1Mo-0.2Si), Ti-1100 (Ti-10.5Al-1.1Sn-2.1Zr-0.2Mo-0.8Si) and four intermetallic compositions: Ti-24Al-11Nb, Ti-24.5Al-17Nb, Ti-24.5Al-17Nb-1Mo and Ti-22Al-23Nb (a%). Ultimate tensile strength of neat [alpha] + [beta] matrices (Timetal[reg sign]21S and Ti-6242S) are high at low temperature, but decrease above 650 C. In addition, they exhibit poor creep performance at 650 C and 760 C. Matrix alloys with continuous alpha-2 phase constituency (Ti-24.5-17 and Ti-24-11) exhibited poor tensile performance across the temperature interval examined (i.e. 23--760 C). In addition, they exhibited poor primary creep resistance, but reasonable creep rupture lives. Significant improvements in both elevated temperature (>650 C) tensile strength and creep performance were observed with increased levels of silicon (Ti-1100) and orthorhombic phase/molybdenum content (Ti-22-23 and Ti-24.5-17-1). Compositional and/or microstructural modification will be required to reach acceptable levels of primary creep performance.

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