α-β titanium alloy refers to a titanium alloy whose annealed structure is (α-β) structure.
According to the difference of molybdenum equivalent, it is divided into martensitic type and transitional type. Molybdenum equivalent 2%-9% is martensitic type, which has high strength and hardness; Molybdenum equivalent 10%-14% is transitional type, which has high strength And plasticity. Typical alloys are titanium-5 aluminum-5 molybdenum-5 vanadium-1 chromium-1 iron and so on.
This kind of alloy has a two-phase structure of α-β type at high temperature, so it is named α+β type titanium alloy. It has good comprehensive mechanical properties, most of which can be strengthened by heat treatment (but TC1, TC2, and TC7 cannot be strengthened by heat treatment), have good forging, stamping and welding properties, can be cut and processed, and have high room temperature strength.
Below 150500 degrees and has good heat resistance, some (such as TC1, TC2, TC3, TC4) have good low temperature toughness and good resistance to seawater stress corrosion and hot salt stress corrosion resistance.
To make the annealed structure of the titanium alloy consist of single-phase α, the additive elements should be mainly α-stabilizing elements. Industrially, the α-β titanium alloy is obtained mainly by adding aluminum, and has a solid solution strengthening effect. Therefore, most of these titanium alloys belong to the Ti-Al series. The alloy element aluminum is added because aluminum has a lower density, which can offset the effect of adding heavy transition metal elements in the alloy on the density of the titanium alloy. Aluminum can remarkably strengthen the α phase at room temperature and high temperature, but if it is added too much, α2 (Ti3Al) phase will appear and cause brittleness. Therefore, the addition of aluminum generally does not exceed 7%.
In order to further improve the performance of the α-β titanium alloy, it is also reported that the Ti-Al alloys are added with neutral elements such as zirconium and tin and a small amount of β-stabilizing elements to form a multi-element composite strengthening, which has a better strengthening effect. This is the so-called near α ferroalloy. The annealed microstructure of this alloy consists of an α-phase matrix and a small amount of β-phase. The presence of a small amount of β phase can improve the press workability, and make the alloy have a certain heat treatment strengthening effect, and can also inhibit the formation of α2 phase.
TA4, TA5, TA6 are mainly used as welding wire materials for titanium alloys. TA7 alloy has good enthusiasm and welding performance, good thermal strength and thermal stability, and can be used to manufacture parts that can work for a long time below 500 ℃. The mechanical properties of TA8 alloy at room temperature and high temperature are higher than those of TA7 alloy. It can work for a long time at 500℃ and can be used to make parts such as engine compressor discs and blades.