Effect of testing atmosphere on cyclic tensile deformation of TiAl-based intermetallic alloys

Abstract

TiAl-based intermetallic alloys with a lamellar microstructure and b containing duplex microstructure were cyclically tensile deformed in various environmental media as a function of temperature. Environmental media used in this study were vacuum, air and a mixture gas of H 2 gasϩAr gas. The environmental embrittlement, i.e., reduction of number of cycles to failure was observed when deformed in air as well as in Ar gas including H 2 gas. The severe environmental embrittlement was observed not only at room temperature but also at ϳ873 K. Fracture patterns and the associated fracture mode were not affected by the environmental media. The possible species causing the environmental embrittlement is suggested to be hydrogen atoms decomposed from water vapor H 2 O or hydrogen gas H 2. The feature observed in the present study was similar in both TiAl-based intermetallic alloys and, also to the previous observation, i.e., the feature of the environmental embrittlement observed in simply tensile deformed specimens.