Formation of the Structure and Properties upon the Aging of a Quenched Alloy Based on Orthorhombic Titanium Aluminide Ti2AlNb Alloyed with Hydrogen

Transmission electron microscopy and microindentation have been used to study the changes in the structure, phase composition, microhardness, and elastic modulus of the Ti–24.3Al–24.8Nb–1.0Zr–1.4V–0.6Mo–0.3Si (at %) alloy based on the orthorhombic titanium aluminide Ti2AlNb alloyed with hydrogen to 8.5 at % upon aging in the temperature range of 600–700°C after quenching from 900°C. It has been detected that the alloying with hydrogen leads to a change in the morphology of precipitated orthorhombic (O) plates upon aging from a zigzag-shaped to packet morphology and at the aging temperature of 700˚С initiates the transformation of the substructure of the O plates into a polydomain one with the formation of the so-called “polysynthetic twin.” The relationship between the structural characteristics, the amounts of the arising phases, and the values of the microhardness and elastic modulus of the investigated alloys with and without hydrogen after quenching and aging has been established.