Titanium has excellent mechanical properties and high specific strength (strength/density ratio), and titanium alloys have better properties; the mechanical properties of titanium and titanium alloys are affected by physical properties, crystal structure and physical properties. is the
titanium crystal structure and phase transitions.
1. Physical properties of titanium crystal structure
Titanium metal has two allotropes, the stable state at low temperature (less than 882.5 degrees) is type, close-packed hexagonal system; the stable state at high temperature is type, body-centered cubic system, the lattice parameter of titanium, at 900 degrees a = 0.33065nm+-0.0000lnm.
The lattice parameters of titanium at 25 degrees Celsius are: a=0.29503nm ± 0.00004nm, c=0.46832nm+-0.00004nm, c/a=1.5873+-0.0004. because. The c/a ratio of titanium is less than the ideal spherical axial ratio of 1.633, so titanium is a malleable metal. The impurities present in titanium have a great influence on its lattice structure. The presence of trace amounts of oxygen and nitrogen will cause the lattice to grow along the c-axis direction, causing an increase in the value, while the a value hardly changes.
2. Physical properties of titanium Phase transition properties
The melting point of titanium is 1668 degrees +-4 degrees. Since molten titanium can interact with almost all refractory materials, it is difficult to measure its latent heat of fusion. The latent heat of fusion of titanium has been measured to range from 15.46 to 20.9 kJ/mol. The surface tension of liquid titanium at the melting point is 1.588N/m, and the dynamic viscosity of liquid titanium at 1730 degrees is 8.9×10 (5th power) m/s. The boiling point of titanium is 3260 degrees +-20 degrees, and the latent heat of vaporization is 428.5 to 470.3 kJ/mol. The critical temperature of titanium is about 4350 degrees, and the critical pressure is 113MPa.
The transformation temperature of the two allotropic forms of titanium is 882.5 degrees Celsius, by. Its volume increase is 5.5%. Oxygen, nitrogen; carbon is a titanium stabilizer. The presence of oxygen, nitrogen and carbon impurities in titanium will increase the phase transition temperature, so that the content of impurities in titanium can be judged according to the change of the transformation temperature, and the crystal transformation of titanium The latent heat is 3.68 to 3.97 kJ/mol.
