Creep of a fine-grained, fully-lamellar, two-phase TiAl alloy at 760{degree}C

Creep of a TiAl alloy, having a composition of Ti-47Al-2Cr-2Nb (in atom %) and a fine-grained, fully-lamellar structure, was carried out at 760 C and stresses between 69--723 MPa. It was found that, in addition to having good room temperature properties, the alloy exhibits higher creep resistance than other TiAl alloys with a similar composition. Both the creep data and microstructures of the alloy suggest that there exists a change in deformation mechanism from a glide-controlled process at high stresses to a recovery-controlled process at low stresses. Also, microstructural evidence indicates that the rate-controlling recovery mechanism is the climb of dislocation segments pinned by ledges at {gamma}/{alpha}{sub 2} interfacial boundaries