Unalloyed, commercially pure titanium exhibits a tensile strength ranging from 275 to 590 MPa. This strength is primarily influenced by the levels of oxygen and iron present in the titanium. Generally, higher oxygen and iron content results in increased strength.
In comparison, commercially alloyed titanium grades can display a much broader range of tensile strength. For example, the alloy Ti-3Al-2.5V has a tensile strength as low as 600 MPa, while high-strength alloys like Ti-15Mo-5Zr-3Al can reach strengths of up to 1250 MPa.
Temperature Stability
Commercially pure titanium maintains stability at temperatures up to approximately 300°C due to its specific strength and creep resistance. More complex titanium alloys can retain high strength even at elevated temperatures, reaching up to 500°C.
Fatigue Strength and Welding
The fatigue strength, defined at 10^7 cycles, is roughly 50% of the tensile strength. One of the key advantages of titanium is that welding does not significantly reduce its fatigue strength. Remarkably, both commercially pure titanium and its alloys show almost no decline in fatigue strength, even when exposed to seawater.
Fracture Toughness
The fracture toughness of titanium alloys ranges from 28 to 108 MPa m^1/2 and exhibits a negative correlation with tensile yield strength. The specific fracture toughness is influenced by the microstructure; alloys with acicular structures tend to have higher fracture toughness.
Understanding these properties is crucial for industries that rely on titanium for applications requiring strength, durability, and resistance to environmental factors.