Room-temperature compressive creep behavior of Ti-6Al-4V ELI alloys with basketweave microstructure under an alternating compressive stress

Titanium alloys have great potential as candidate materials for the deep-sea facilities. Long-term creep deformation behavior of the pressure-bearing structures made of titanium alloys under alternating compressive stress has a direct impact on the structural stability. The compressive creep evaluations of Ti-6Al-4V ELI alloys with basketweave microstructure under alternating stresses have been carried out by a uniaxial compressive creep tester. The compressive creep deformations have strong stress sensitivity due to the larger creep strain by the higher applied compressive stress. The dislocation densities in α and β phases increase with the increase of applied compressive stresses. The dislocation slip and dislocation multiplication occur in α phases accompanying with high dislocations density in β phases caused by compressive deformation. The large strain concentration occurs at the grain boundaries of α/β phase due to dislocation plug after creep, which causes the grain boundary pinning. The compressive creep deformation of Ti-6Al-4V ELI alloys under alternating stress is a decelerating creep process and controlled by dislocation slip. The slight refinements of the grains and hardening have been confirmed after creeps. The synergistic effects of dislocation multiplication, grain boundary pinning and grain refinements lead to strengthening the Ti-6Al-4V ELI alloys and decelerating the compressive creeps.