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The tensile strength of pure titanium is 265-353MPa, and that of general titanium alloys is 686-1176MPa, currently up to 1764MPa. The strength of titanium alloys is equivalent to that of many steels, but the specific strength of titanium alloys is much better. The specific strength here refers to the strength of the material divided by its apparent density, also known as the strength-to-weight ratio. The international unit of specific strength is (N/m2)/(kg/m3) or N·m/kg. The ratio of the tensile strength of a material to the apparent density of the material is called specific strength. The ratio of a material’s strength (tensile) to density at its breaking point.

The compressive strength of titanium and titanium alloys is not less than its tensile strength. The compressive yield strength and tensile yield strength of industrial pure titanium are approximately equal, while the compressive strength of Ti-6Al-4V and Ti-5Al-2.5Sn alloys is slightly higher than the tensile strength. The shear strength is generally 60%-70% of the tensile strength. The pressure-bearing yield strength of titanium and titanium alloy sheets is 1.2-2.0 times the tensile strength.

Under normal atmospheric atmosphere, the lasting strength of processed and annealed titanium and titanium alloys is (0.5-0.65) times the tensile strength. When 107 fatigue tests were performed in the notched state (Kt=3.9), the lasting strength of annealed Ti-6Al-4V was 0.2 times the tensile strength.

The highest purity grade of machined industrial pure titanium usually has a hardness of less than 120HB, and other purity grades of machined titanium have a hardness of 200-295HB. The hardness of pure titanium castings is 200-220HB. The hardness value of titanium alloy in the annealed state is 32-38HRC, which is equivalent to 298-349HB. The hardness of as-cast Ti-5Al-2.5Sn and Ti-6Al-4V alloys is 320HB, and the hardness of low-gap impurity Ti-6Al-4V castings is 310HB.

The tensile elastic modulus of industrial pure titanium is 105-109GPa, and the tensile elastic modulus of most titanium alloys in the returned state is 110-120GPa. Age-hardened titanium alloys have a slightly higher tensile elastic modulus than in the annealed state, and the compressive elastic modulus is equal to or greater than the tensile elastic modulus. Although the stiffness of titanium and titanium alloys is much higher than that of aluminum and aluminum alloys, it is only 55% of iron. The specific elastic modulus of titanium alloys is comparable to that of aluminum alloys, second only to beryllium, molybdenum and some high-temperature alloys.

The torsion or shear modulus of industrial pure titanium is 46GPa, and the shear modulus of titanium alloy is 43-51GPa.

In order to improve the strength of titanium alloys, increasing the content of interstitial elements will have harmful effects on the impact resistance and fracture toughness of the alloys. Depending on the type and state of the titanium alloy, the Charpy notch impact strength value of pure titanium in the processing industry is 15-54J/cm2, and that in the cast state is 4-10J/cm2. The impact strength of titanium alloy in the annealed state is 13-25.8J/cm2, and that in the aged state is slightly lower. The Charpy V-notch impact strength of the Ti-5Al-2.5Sn alloy in the cast state is 10J/cm2, and that of the Ti-6Al-4V alloy is 20-23J/cm2. The lower the oxygen content of titanium alloy processing materials, the higher this value.

Many titanium alloys have high fracture toughness, or in other words, titanium alloys are very resistant to crack propagation. The annealed Ti-6Al-4V alloy is a material with excellent toughness. When the notch concentration coefficient Kt=25.4mm, the ratio of notched tensile strength to non-notched tensile strength is greater than 1.

Titanium alloys can maintain certain properties at high temperatures. Generally, industrial titanium alloys can maintain their useful properties at a temperature of 540°C, but they can only be used for short periods of time. The temperature range for long-term use is 450-480°C. Titanium alloys for use at temperatures of 600°C have been developed. As a missile material, titanium alloy can be used at a temperature of 540°C for a long time and at a temperature of 760°C for a short time.

Titanium and titanium alloy materials can still maintain certain original mechanical properties at low and ultra-low temperatures. As the temperature decreases, the strength of titanium and titanium alloy materials continues to increase, while the ductility gradually becomes worse. Many annealed titanium alloy materials have sufficient ductility and fracture toughness at -195.5°C. The Ti-5Al-2.5Sn alloy containing very few interstitial elements can be used at a temperature of -252.7°C. The ratio of its notched tensile strength to non-notched tensile strength is 0.95-1.15 at -25.7°C.

Liquid oxygen, liquid hydrogen and liquid fluorine are important propellants in missiles and space devices. The low-temperature properties of materials used to make cryogenic gas containers and cryogenic structural parts are very important. When the microstructure is equiaxed and the content of interstitial elements (oxygen, nitrogen, hydrogen, etc.) is very low, the ductility of titanium alloys is still above 5%. Most titanium alloys have poor ductility at -252.7°C, while the elongation of Ti-6Al-4V alloy can reach 12%.