Moisture-induced embrittlement of B2-type CoTi ordered intermetallics

B2-type CoTi ordered intermetallics with various micro structures was tensile tested at room temperature in air and vacuum. Moisture-induced embrittlement was assessed by tensile properties and fracture behavior. Irrespective of microstructures, tensile elongation and strength of the specimen deformed in air were lower than those of the specimen deformed in vacuum, while yield strength was similar in both air and vacuum. SEM observation for the specimens with deformed and unrecrystallized microstructures showed that the quasi-cleavage fracture mode was dominant irrespective of testing environment. However, the specimen with fully recrystallized microstructure showed quasi-cleavage fracture mode mixed with intergranular fracture mode. Strain rate did not affect the fracture mode as well as the tensile properties. On the other hand, the extent of embrittlement was lower in the pre-strained specimen as well as the specimens with deformed and unrecrystallized microstructures than in the specimen with fully recrystallized microstructure. The results showed that the moisture-induced embrittlement of CoTi ordered intermetallics was influenced by microstructures including lattice defects.