High-temperature environmental embrittlement of thermomechanically processed TiAl-based intermetallic alloys

Abstract

Thermomechanically processed TiAl-based intermetallic alloys with various alloy compositions and microstructures were tensile tested in various environmental media, including air, water vapor, and a gas mixture of 5 vol pct, H2 + Ar, as functions of temperature and strain rate. All the TiAl-based intermetallic alloys showed reduced tensile fracture stress (or elongation) in air, in water vapor, and in a gas mixture of 5 vol pct H2 + Ar, not only at ambient temperature (RT ∼ 600 K), but also at high temperature, from 600 to 1000 K (and sometimes at temperatures higher than 1000 K). The high-temperature environmental embrittlement of TiAl-based intermetallic alloys depended upon the microstructure. The factors causing the high-temperature environmental embrittlement may include hydrogen atoms decomposed from water vapor (H2O) or hydrogen gas (H2), similar to those causing the low-temperature environmental embrittlement. Also, it is demonstrated that the oxidized scale is effective in reducing high-temperature environmental embrittlement.