Ferrotitanium Alloy

►Alloying elements can be divided into three categories according to their effect on the 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. Among them, aluminum is the main alloying element of titanium alloy, which has obvious effect on improving the strength of alloy at room temperature and high temperature, reducing the specific gravity and increasing the elastic modulus.

② The elements that stabilize β phase and reduce the phase transition temperature are β stable elements, which can be divided into isomorphic and eutectoid types. The former has molybdenum, niobium, vanadium and so on; The latter has chromium, manganese, copper, iron, silicon and so on.

③ The elements that have little effect on the phase transition temperature are neutral elements, such as zirconium and tin.Oxygen, ammonia, carbon and hydrogen are the main impurities of titanium alloys. Oxygen and nitrogen have a large solubility in the α phase, which has a significant strengthening effect on titanium alloy, but it reduces the plasticity. It is usually stipulated that 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 a phase is very small, and too much hydrogen dissolved in titanium alloys will produce hydrides, making the alloy brittle. Generally, the hydrogen content in titanium alloys is controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing.