Mechanical functions of titanium and titanium alloy processing!

Release time：2022-11-23 15:21:49 丨 Number of visits：

The tensile strength of pure titanium is 265-353MPa, and the general titanium alloy is 686-1176MPa, now up to 1764MPa. Titanium alloy and many steel strength is comparable, but much better than the strength of titanium alloy, where the specific strength refers to the strength of the data divided by its apparent density, also known as strength-weight ratio. The SI 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. Ratio of strength to density of data at cracking point.

The compressive strength of titanium and titanium alloys is not less than the tensile strength. The compressive yielding strength and tensile yielding 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 compressive yield strength of titanium and titanium alloy sheet is 1.2-2.0 times of the tensile strength.

The endurance strength of machined and annealed titanium and titanium alloys is (0.5-0.65) times tensile strength under normal atmosphere. The endurance strength of annealed Ti-6Al-4V is 0.2 times of tensile strength when 107 fatigue tests are carried out in notched condition (Kt=3.9).

High purity grade processed industrial pure titanium is usually less than 120HB hardness, other purity processed titanium hardness is 200-295HB. The hardness of pure titanium castings is 200-220HB. The hardness of titanium alloy in annealed condition is 32-38HRC, which is equivalent to 298-349HB. The hardness of Ti-5Al-2.5Sn and Ti-6Al-4V alloys as cast is 320HB, and the hardness of Ti-6Al-4V castings with low void impurities is 310HB.

The tensile modulus of industrial pure titanium is 105-109GPa, and most titanium alloys have a tensile modulus of 110-120GPa in the returned condition. The age-hardened titanium alloy has a slightly higher tensile modulus than the annealed 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% that of iron. The specific elastic modulus of titanium alloy is similar to that of aluminum alloy, only second to beryllium, molybdenum and some superalloys.

The torsional or shear modulus of industrial pure titanium is 46GPa and that of titanium alloy is 43-51GPa.

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

Many titanium alloys have very high cracking toughness, or very good resistance to crack growth. The annealed Ti-6Al-4V alloy is one of the materials with excellent endurance. When the notch concentration coefficient Kt=25.4mm, the ratio of notch tensile strength to non-notch tensile strength is greater than 1.

Titanium alloy can also maintain certain functions at high temperature. General industrial titanium alloy can adhere to its useful function at 540℃ temperature, but only for short time applications, long-term application of the temperature range of 450-480℃. Titanium alloys have been developed for use at 600℃. Titanium alloy as missile data can be used at 540℃ temperature for a long time, but also can be used at 760℃ temperature for a short time.

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

Liquid oxygen, liquid hydrogen and liquid fluorine are important propellants in missiles and world equipment. The low temperature function of the data used in the manufacture of low temperature gas containers and low temperature structural parts is very important. When the microstructure is equiaxed and the content of void 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℃, but the elongation of Ti-6Al-4V alloy can reach 12%.