Titanium alloys can be divided into heat resistant alloys, high strength alloys, corrosion resistant alloys (titanium-Molybdenum, titanium-palladium alloys, etc.), cryogenic alloys and special functional alloys (titanium-iron hydrogen storage materials and titanium-Nickel memory alloys).The composition and properties of typical alloys are shown in the table.
Different phase composition and microstructure can be obtained by adjusting the heat treatment process. It is generally believed that the fine equiaxed structure has better plasticity, thermal stability and fatigue strength. The spicules have high durable strength, creep strength and fracture toughness. The equiaxed and acicular mixed tissues have better comprehensive properties.
The commonly used heat treatment methods include annealing, solid solution and aging treatment. Annealing is to eliminate internal stress, improve plasticity and microstructure stability, and obtain better comprehensive performance. Generally, the annealing temperature of alloy and (+) alloy is 120 ~ 200℃ below (+) -- → phase transition point.The solid solution and aging treatment is rapid cooling from the high temperature region to obtain the martensite 'phase and the metastable phase, and then the heat preservation in the medium temperature region causes the decomposition of these metastable phases, and the second phase particles such as the phase or compounds are obtained to strengthen the alloy. Usually (alpha + beta) alloy quenching in alpha + beta) -- - > beta phase transition point below 40 ~ 100 ℃, metastable beta alloy quenching in alpha + beta) -- - > beta phase transition point above 40 ~ 80 ℃.Aging treatment temperature is generally 450 ~ 550℃.In addition, in order to meet the special requirements of the workpiece, the industry also adopts double annealing, isothermal annealing, heat treatment, deformation heat treatment and other metal heat treatment process.
