Primary creep and anelastic recovery of a near γ-TiAl intermetallic

The primary creep behaviour of a binary near gamma-Ti-48at%Al intermetallic heat treated to the duplex or two fully lamellar microstructures is investigated. The results from monotonic creep tests at 760 degrees C are presented, along with tests involving a 90% stress reduction following primary creep at a stress of 240 MPa to controlled strain levels between 0.2 and 0.8% strain. The anelastic recovery following the stress reduction is analyzed as a function of the microstructure and the applied forward creep strain. The primary creep resistance is improved by changing the microstructure from the duplex to fully lamellar conditions. Anelastic recovery occurs in two stages. The first stage lasts approximate to 100 seconds and is characterized by a relatively high strain rate and is thought to occur by reverse dislocation glide. The kinetically slower second stage (requiring up to 10(5) seconds) is thought to occur by non-conservative dislocation motion. The results are consistent with the supposition that forward creep at 240 MPa/760 degrees C occurs via a dislocation glide process.