The advantages of titanium
Titanium compared with other metal materials, has the following advantages:
① high specific strength (tensile strength / density) (see photo), the tensile strength of up to 100 ~ 140kgf / mm2, and the density of only 60% of steel.
② medium temperature strength, the use of high temperature than the aluminum hundreds of degrees, at moderate temperatures can still maintain the required strength, at 450 ~ 500 ℃ temperature long-term work.
③ good corrosion resistance, the titanium surface in the atmosphere immediately formed a uniform and dense oxide film, a resistance to erosion of a variety of media capabilities. Titanium is generally corrosion-resistant in oxidizing and neutral media and offers superior corrosion resistance in seawater, wet chlorine and chloride solutions. However, in reducing media, such as hydrochloric acid and other solutions, titanium corrosion resistance is poor.
④ low temperature performance, low gap element titanium alloy, such as TA7, at -253 ℃ can maintain a certain degree of plasticity.
⑤ low modulus of elasticity, thermal conductivity, non-ferromagnetic.
7. Punching poor, thermoplastic good.
Heat Treatment Titanium alloys can be obtained by adjusting the heat treatment process of different phase composition and organization. Generally believed that fine equiaxial tissue has better plasticity, thermal stability and fatigue strength; acicular tissue has a higher long-lasting strength, creep strength and fracture toughness; equiaxed and needle-like hybrid tissue has good overall performance.
Commonly used heat treatment methods are annealing, solution and aging treatment. Annealing is to eliminate internal stress, improve plasticity and tissue stability, in order to obtain better overall performance. Usually α alloy and (α + β) alloy annealing temperature selected (α + β) - → β phase transition point 120 ~ 200 ℃; solution and aging treatment is rapidly cooled from the high temperature to obtain martensite α ' Phase and metastable β phase, and then in the temperature zone so that these metastable phase decomposition, the α-phase or compounds were fine particles of the second phase to achieve the purpose of strengthening the alloy. Quenching the (α + β) alloy is usually performed at 40 to 100 ° C below the (α + β) - β transformation point, and the metastable β alloy is quenched at 40 to 80 ° C above the (α + β) get on. Aging treatment temperature is generally 450 ~ 550 ℃. In addition, in order to meet the special requirements of the workpiece, the industry also uses double annealing, isothermal annealing, β heat treatment, heat treatment and other metal deformation heat treatment process.