Room-temperature Compressive Creep Behavior of Ti-6Al-4V ELI Alloys with a Basketweave Microstructure under Alternating Compressive Stresses

Titanium alloys have great potential as candidate materials for 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 structural stability. The compressive creep evaluations of Ti-6Al-4V extra low interstitial (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 accompanied by 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 <a> dislocation slip. The slight refinements of the grains and hardening have been confirmed after creep. 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 creep.