Titanium and titanium alloys have high specific strength and excellent corrosion resistance, which are called "ocean metals" and are ideal structural materials in the field of ocean engineering manufacturing. The crew capsules of the Sea Cliff and Alvin submersibles were gradually replaced with titanium alloys at a later stage. At present, TI-6AL-4V titanium alloy of 800 MPa strength level is basically adopted in the mainstream manned submersible in the world, including "Jiaolong" and "deep-sea Warrior" manned submersible developed during the "Eleventh Five-Year plan" and "Twelfth Five-Year Plan"
Consistent with the requirements of aviation and aerospace on structural weight reduction, the structural weight reduction benefits of deep-sea equipment are obvious. After weight reduction, the navigation agility of Marine exploration equipment can be increased, the amount of buoyant materials can be reduced, energy consumption can be reduced, and the operation cycle of equipment can be improved.
Titanium alloy structure weight reduction design require the use of higher strength, but structure strength - the material toughness "upside down" phenomenon, enhance strength after often results in the decrease of toughness, lead to brittle fracture and reduce the reliability and service life of structure, therefore, both high strength and high toughness titanium alloy is often the bottleneck problem of equipment development.