Microstructure Sensitivity on Environmental Embrittlement of a High Nb Containing TiAl Alloy under Different Atmospheres

Abstract

Mechanical properties in different atmospheres, including oxygen, vacuum, air and H2, of high Nb containing TiAl alloys with the compositions of Ti–45Al–8.5Nb–(0.2W, 0.2B, 0.02Y) have been investigated in this work. Three different microstructure types, nearly lamellar, gamma phase increased nearly lamellar and fully lamellar are selected for revealing the microstructure sensitivity of environmental embrittlement. The results show that the three types of microstructures are all affected by the hydrogen–induced environmental embrittlement. Although the fracture mode of the experimental alloy is cleavage fracture in all atmospheres, the proportions of transgranular and intergranular fractures are different, especially comparing the fracture surfaces in oxygen and hydrogen. Performance comparison results show that the nearly lamellar microstructure is the most susceptible to the hydrogen–induced environmental embrittlement, while the gamma phase increased microstructure is the most stable one; the fully lamellar microstructure results in moderate susceptibility to the atmospheres. Combined with the hydrogen absorption kinetic analysis, it indicates that γ phase at the interface of lamellar colony significantly inhibits the hydrogen–induced environmental embrittlement, while the effect of β phase is just the opposite. In addition, the correlation between microstructure and hydrogen–induced environmental embrittlement is revealed and the corresponding mechanism is also discussed in this work.

Effect of Hydrogen Charging on the Mechanical Properties of High-Strength Copper-Base Alloys, Austenitic Stainless Steel AISI 321, Inconel 625 and Ferritic Steel 1.4511

“…Damage might emerge during manufacturing or as delayed fracture when a hydrogen-containing component is put under operating stresses. Hydrogen Environmental Embrittlement (HEE) is the most common form of HE [8,9,[13][14][15]. Hydrogen is either generated due to contact with aqueous solutions as a product of corrosion processes (cathodic stress corrosion cracking) or by a gaseous atmosphere such as pressurized hydrogen.…”

The Role of Boron Addition on Solidification Behavior and Microstructural Evolution of a High Niobium-Containing TiAl Alloy

“…Therefore, the aluminum content should not be too high for TiAl alloys [11]. As for the alloying process, for Nb alloying and the development of high Nb-containing TiAl alloys, compared with ordinary TiAl alloys, its service temperature can be increased by 60~100 • C, the high-temperature yield strength is doubled and the hightemperature oxidation resistance is also greatly improved [12,13]. In addition, the addition of the Nb element can reduce the stacking fault energy of γ phase in TiAl alloy, which is conducive to the opening of deformation twins, thereby reducing the room temperature brittleness of the alloy [14].…”

Corrosion and Mechanical Behavior of Metal Materials

“…From the point view of materials and structures, failure can be caused by the unique mechanical and corrosive environment during their service life. The research methods of most forward environmental fractures [4,19,20] and the new mechanical analysis techniques for structures could all be useful in the study of those particular failure behaviors. Hence, this Special Issue, entitled "Corrosion and Mechanical Behavior of Metal Materials", will mainly concentrate on how high-strength metal materials and structures work under the conditions of corrosion and complex loading.…”