Classification of titanium alloys

Titanium alloy is an alloy based on titanium and composed of different elements. There are two kinds of homogenous heterocrystals of titanium: close-packed hexagonal α titanium below 882℃, and body-centered cubic β titanium above 882℃.

Titanium Pipes alloy elements can be classified into three categories based on their effect on phase transition temperature:

① The elements that stabilize the α phase and increase the phase transition temperature are the α stable elements, including aluminum, carbon, oxygen and nitrogen. Aluminum is the main alloying element of titanium alloy, which has an obvious effect on improving the strength of alloy at room temperature and elevated temperature, reducing specific gravity and increasing elastic modulus.

② The elements that stabilize β phase and reduce the temperature of phase transformation are β stable elements, which can be divided into two types: crystalline type and eutectic type. The application of titanium products the former molybdenum, niobium, vanadium and so on; ​the latter has chromium, manganese, copper, iron, silicon and so on.

③ The elements that have slight effect on the temperature of phase transition are neutral elements, such as zirconium and tin.

Oxygen, nitrogen, carbon and hydrogen are the main impurities of titanium alloy. The elevated solubility of oxygen and nitrogen in the α phase strengthens titanium alloy significantly, but decreases the ductility. ​Typically, the content of oxygen and nitrogen in titanium is below 0.15 ~ 0.2% and 0.04 ~ 0.05%, respectively. The solubility of hydrogen in the alpha phase is extremely tiny, and overly much hydrogen dissolved in titanium alloy will produce hydrides, making the alloy brittle. ​Typically, the hydrogen content of titanium alloys is controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing.

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