The tensile strength of pure titanium is 265 ~ 353MPa, and the general titanium alloy is 686 ~ 1176MPa, and the current maximum can reach 1764MPa. Titanium alloys are comparable in strength to many steels, but the specific strength of steels is far less than titanium alloys....
The tensile strength of pure titanium is 265 ~ 353MPa, and the general titanium alloy is 686 ~ 1176MPa, and the current maximum can reach 1764MPa. Titanium alloys are comparable in strength to many steels, but the specific strength of steels is far less than titanium alloys.
The compressive strength of titanium and titanium alloys is not lower than their tensile strength. The compressive and tensile yield strengths of industrial pure titanium are approximately equal, while the compressive strengths of Ti-6AI-4V and Ti-5AI-2.5Sn are slightly higher than the tensile strengths.
The shear strength is generally 60% to 70% of the tensile strength. The compressive yield strength of titanium and titanium alloy sheets is approximately 1.2 to 2.0 times the tensile strength.
Under normal atmospheric atmosphere, the endurance limit of processed and annealed titanium and titanium alloys is 0.5 to 0.65 tensile strength. The endurance limit of annealed Ti-6AI-4V is 0.2 times the tensile strength when subjected to 10 million fatigue tests in the notched state (Kt = 3.9).
The hardness of the highest purity grade processed industrial pure titanium is usually less than 120HB (Brinell hardness), and the hardness of other industrial pure processed titanium is 200 to 295HB. The hardness of pure titanium castings is 200-220HB. The hardness value of titanium alloy in the annealed state is 32-38HRC (Rockwell), which is equivalent to 298-349HB. The hardness of the as-cast Ti-5Al-2.5Sn and Ti-6AI-4V is 320HB, and the hardness of the low interstitial impurity Ti-6Al-4V casting is 310HB.
The tensile elastic modulus of industrial pure titanium is 105 to 109 GPa. The tensile elastic modulus of most titanium alloys in the annealed state is 110 to 120 GPa. The age-hardened titanium alloy has 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. The specific elastic modulus of titanium alloy is equal to that of aluminum alloy, second only to beryllium, molybdenum and some superalloys.
The torsional 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 interstitials will have a detrimental effect on the impact resistance and fracture toughness of the alloy. Depending on the type and state of titanium alloys, the Charpy notched impact strength of denatured industrial pure titanium is 15-54J/㎡, and about 4-10J/㎡ in the cast state. The impact strength of the titanium alloy in the annealed state is 13-25.8J/㎡, and the aging state is slightly lower. The Charpy V-notch impact strength of the as-cast Ti-5AI-2.5Sn is 10J/㎡, and that of the Ti-6AI-4V is 20-23J/㎡. The lower the oxygen content of titanium alloys, the higher the value.
Many titanium alloys have high fracture toughness, or the ability of titanium alloys to resist crack propagation is very good. The annealed Ti-6AI-4V is a material with excellent toughness. When the notch concentration factor 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. General industrial titanium alloys can maintain their properties at a temperature of 540 °C, but only for short-term applications, and the temperature range for a long time is 450-480 °C. Titanium alloys for use at temperatures up to 600°C have been developed. As a missile material, titanium alloy can be used for a long time at a temperature of 540 °C, and can also be used for a short time at a temperature of 760 °C. The high temperature properties of several titanium alloys are shown in Table 2-7.
⑩Titanium and titanium alloys can still maintain their original mechanical properties at low and ultra-low temperatures. As the temperature decreases, the strength of titanium and titanium alloys increases continuously, while the ductility gradually deteriorates. Many annealed titanium alloys also have sufficient ductility and fracture toughness at -195.5°C. Ti-5AI-2.5Sn with extra low interstitial elements can be used at -252.7℃. The ratio of its notched tensile strength to unnotched tensile strength is 0.95 to 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 low temperature gas containers and low temperature structures are very important. When the microstructure is equiaxed and the content of interstitial elements (oxygen, helium, 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 Ti-6AI-4V reaches 12% elongation.
