Creep deformation behavior of three high-temperature near alpha-Ti alloys:IMI 834, IMI 829, and IMI 685

The steady-state and transient creep properties of three high-temperature, near alpha -Ti alloy-IMI 834, IMI 829, and IMI 685-have been investigated i n constant-stress tensile creep. The creep tests were conducted on the as-r eceived microstructures, i.e., a duplex microstructure with 17 pct primary a for IMI 834 and fully transformed microstructures for IMI 829 and 685. Th e results show that both steady-state and transient creep rates follow powe r-law creep, with stress exponents in the range from 4.2 to 5.2 for the ste ady-state and from 3.2 to 6.2 for the transient creep rates. The activation energies obtained decrease, in order, from IMI 834 to IMI 685 and take the values of 345, 329, and 304 kJ/mol, respectively. The creep mechanisms are discussed in light of the creep microstructures, the stress-dip experiment s and activation energy being probably controlled by the climb of pinned ne twork dislocations. The high activation energies obtained are thought to ar ise from alloying effects.