Creep deformation behavior of three high-temperature near α-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 in constant-stress tensile creep. The creep tests were conducted on the as-received microstructures, i.e., a duplex microstructure with 17 pct primary a for IMI 834 and fully transformed microstructures for IMI 829 and 685. The results show that both steady-state and transient creep rates follow power-law creep, with stress exponents in the range from 4.2 to 5.2 for the steady-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 experiments and activation energy being probably controlled by the climb of pinned network dislocations. The high activation energies obtained are thought to arise from alloying effects.