High-temperature tensile properties and fracture characteristics in a monolithic gamma TiAl alloy and a TiB2 particle-reinforced TiAl alloy

Extensive research and development has identified several two-phase (gamma-TiAl+alpha(2)-Ti3Al) gamma TiAl alloys based on Ti-(45-48 at. pct)Al. The gamma alloys reinforced with TiB2 particles via the XD process have emerged as a potential engineering alloy group owing to their unique mechanical properties. In this study, a monolithic gamma TiAl alloy and a TiB2 particle-reinforced TiAl alloy were selected to assess their high-temperature tensile properties and fracture behavior. The two alloys evaluated had nominal compositions (at. pct) of Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si (designated WMoSi alloy) and Ti-45Al-2Nb-2Mn + 0.8 vol. pct TiB2 XD processed (designated XD alloy). The alloy ingots were arc-melted in a vacuum and cast into cylindrical bars 14 mm in diameter. The cast alloy bars were HIPed at 1260 C for 4 h under a pressure of 172 MPa and then annealed at 1010 C for 50 h in an argon atmosphere, followed by air cooling. Tensile tests were performed on the specimens, and plots of yield strength vs. temperature and elongation vs. temperature are presented for both the WMoSi and XD alloys. In addition, micrographs of both alloys are shown after HIPing, and SEM fractographs of the alloys are presented after testing at 538 C and 871 C. (AIAA)