Effect of microstructure on creep and creep crack growth behaviour of titanium alloy

Abstract

Creep and creep crack growth behaviour of a near α titanium alloy has been investigated at 600°C which is affected by primary α content. The alloy was heat treated at different temperatures so as to obtain different levels of equiaxed primary α in the range from 5 to 24 %. Constant load creep tests were carried out at 600°C in the stress range 250 to 400 MPa till rupture of the specimens. Creep crack growth tests were carried out at 600°C. Creep data reveals with increase in primary α content leads to creep weakening. On similar lines maximum creep crack growth resistance is associated with the alloy with lowest primary α content. Microstructural and fractographic examination has revealed that creep fracture occurs by nucleation, growth and coalescence of microvoids nucleated at primary β / transformed β (matrix) interfaces. On the other hand, creep crack growth occurs by surface cracks nucleated by fracture of primary α particles as well as by growth and coalescence of microvoids nucleated at primary β / transformed β (matrix) interfaces in the interior of the specimen.

In-Situ SEM Observation on Fracture Behavior of Titanium Alloys with Different Slow-Diffusing β Stabilizing Elements

“…In general, microstructure plays an important role in the mechanical properties of titanium alloys, such as strength, ductility, creep resistance and fracture toughness [12,13]. Usually, the bimodal microstructure of the primary α phase (α p ) and the transformed β phase (β t ) typically exhibit good room-temperature ductility and high-temperature strength.…”