High-Temperature Environmental Embrittlement of Thermomechanically Processed TiAl-Based Intermetallic Alloys with Various Kinds of Microstructures

Abstract

ABSTRACTThermomechanically processed TiAl-based intermetallic alloys with various alloy compositions and microstructures were tensile tested in various environmental media including air, water vapor and a mixture gas of 5vol.%H2+Ar as a function of temperature. All the TiAl-based intermetallic alloys showed reduced tensile fracture stress (or elongation) in air, water vapor and a mixture gas of 5vol.%H2+Ar not only at ambient temperature (RT∼600K) but also at high temperature mostly from 600K to 1000K (sometimes higher temperature than 1000K). The high-temperature environmental embrittlement of TiAl-based intermetallic alloy depended upon the microstructure. The possible species causing the high-temperature environmental embrittlement are hydrogen atoms decomposed from water vapor (H2O) or hydrogen gas (H2), similar to those causing the low-temperature environmental embrittlement.