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Mechanical function of titanium and titanium alloy processing!

更新时间  2022-12-14 16:28:40

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


The compression strength of titanium and titanium alloys shall not be lower than their tensile strength. The compressive yield strength and tensile yield strength of industrial pure titanium are roughly 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 bearing yield strength of titanium and titanium alloy sheet is 1.2-2.0 times of the tensile strength.


Under normal atmospheric atmosphere, the durability of titanium and titanium alloy after processing and annealing is (0.5-0.65) times of tensile strength. When 107 fatigue tests were conducted in notch condition (Kt=3.9), the endurance strength of annealed Ti-6Al-4V was 0.2 times of tensile strength.


The hardness of high purity processing industrial pure titanium is usually less than 120HB, and the hardness of other purity processing titanium is 200-295HB. The hardness of pure titanium casting is 200-220HB. The hardness value of titanium alloy under annealing condition is 32-38HRC, which is equivalent to 298-349HB. The hardness of as cast Ti-5Al-2.5Sn and Ti-6Al-4V alloy is 320HB, and the hardness of low void impurity Ti-6Al-4V casting is 310HB.


The tensile elastic modulus of commercial pure titanium is 105-109GPa, and that of most titanium alloys is 110-120GPa under the return condition. The age hardened titanium alloy has a slightly higher tensile elastic modulus than the annealed titanium alloy, 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 that of iron. The specific elastic modulus of titanium alloy is equivalent to that of aluminum alloy, only inferior to beryllium, molybdenum and some superalloys.


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


In order to improve the strength of titanium alloys, the addition of void elements will have harmful effects on the impact resistance and cracking toughness of the alloys. According to the different types and conditions of titanium alloys, the Charpy notch impact strength of processing industrial pure titanium is 15-54J/cm2, and that of casting is 4-10J/cm2. The impact strength of titanium alloy in the annealed condition is 13-25.8J/cm2, and the aging condition is slightly lower. The Charpy V-notch impact strength of Ti-5Al-2.5Sn alloy in casting condition is 10J/cm2, and that of Ti-6Al-4V alloy is 20-23J/cm2. The lower the oxygen content is, the higher this value is.


Many titanium alloys have very high crack toughness, or they can resist crack propagation very well. The annealed Ti-6Al-4V alloy is an excellent material for resistance. When the notch concentration factor Kt=25.4mm, the ratio of notch tensile strength to non notch tensile strength is greater than 1.


Titanium alloys can still hold certain functions at high temperatures. General industrial titanium alloys can adhere to their useful functions at 540 ℃, but can only be used for a short time. The temperature range for long-term use is 450-480 ℃. The titanium alloy used at 600 ℃ has been developed. As missile data, titanium alloy can be used at 540 ℃ for a long time and 760 ℃ for a short time.


Titanium and titanium alloy materials can still adhere to their original mechanical functions at low temperature and ultra-low temperature. With the decrease of temperature, the strength of titanium and titanium alloy materials is continuously increased, while the ductility is gradually deteriorated. Many annealed titanium alloys have sufficient ductility and cracking toughness at - 195.5 ℃. Ti-5Al-2.5Sn alloy with very few interstitial elements can be used at - 252.7 ℃. The ratio of notched tensile strength to non notched tensile strength is 0.95-1.15 at - 25.7 ℃.


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