Long-term hardness of eutectic alloys of the Ti−Ga−Si system in the high-titanium region

Titanium intermetallides (Ti sub 3 Al, TiAl and TiAl sub 3 ) are of great interest for aircraft structural alloys because of good heat-resistance, oxidation-resistance, and corrosion- resistance. Extensive studies have been made of the alloy system Ti-Ga-Si (by the authors) because Ga is a stabilizer for alpha-Ti, which raises the Ti alpha-beta transformation by 50 deg C, so the presence of Ga will not lower the melting point of Ti. High temperature hardness measurements were made for evaluation of mechanical properties (as described and discussed in detail in this article). Maximum heat resistance is exhibited by alloys 1 and 2 (which are characterized by high phase-transformation temperatures and highly dispersed strengthening phases (Ti sub 2 Ga and Ti sub 5 (Si,Ga) sub 3 )). Thus, it was established that (at temperatures up to 0.6 T sub (melt) , the long-term hardness of eutectic alloys in the Ti-Ga- Si is twice as grdening from fine particles of high-melting phases and the transition from a one-phase structure to a two-phase composite microstructure.