Titanium alloy

Titanium alloys are metals that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures). They are light in weight, have extraordinary corrosion resistance and the ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to military applications, aircraft, spacecraft, bicycles, medical devices, jewelry, highly stressed components such as connecting rods on expensive sports cars and some premium sports equipment and consumer electronics.'Alloys may be supplied in the following conditions: Grades 5, 23, 24, 25, 29, 35, or 36 annealed or aged; Grades 9, 18, 28, or 38 cold-worked and stress-relieved or annealed; Grades 9, 18, 23, 28, or 29 transformed-beta condition; and Grades 19, 20, or 21 solution-treated or solution-treated and aged.''Note 1—H grade material is identical to the corresponding numeric grade (that is, Grade 2H = Grade 2) except for the higher guaranteed minimum UTS, and may always be certified as meeting the requirements of its corresponding numeric grade. Grades 2H, 7H, 16H, and 26H are intended primarily for pressure vessel use.''The H grades were added in response to a user association request based on its study of over 5200 commercial Grade 2, 7, 16, and 26 test reports, where over 99% met the 58 ksi minimum UTS.''This alpha-beta alloy is the workhorse alloy of the titanium industry. The alloy is fully heat treatable in section sizes up to 15 mm and is used up to approximately 400 °C (750 °F). Since it is the most commonly used alloy – over 70% of all alloy grades melted are a sub-grade of Ti6Al4V, its uses span many aerospace airframe and engine component uses and also major non-aerospace applications in the marine, offshore and power generation industries in particular.''Applications: Blades, discs, rings, airframes, fasteners, components. Vessels, cases, hubs, forgings. Biomedical implants.'Bio compatibility: Excellent, especially when direct contact with tissue or bone is required. Ti-6Al-4V's poor shear strength makes it undesirable for bone screws or plates. It also has poor surface wear properties and tends to seize when in sliding contact with itself and other metals. Surface treatments such as nitriding and oxidizing can improve the surface wear properties.Ti6Al7Nb is a dedicated high strength titanium alloy with excellent biocompatibility for surgical implants. Used for replacement hip joints, it has been in clinical use since early 1986. Titanium alloys are metals that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures). They are light in weight, have extraordinary corrosion resistance and the ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to military applications, aircraft, spacecraft, bicycles, medical devices, jewelry, highly stressed components such as connecting rods on expensive sports cars and some premium sports equipment and consumer electronics. Although 'commercially pure' titanium has acceptable mechanical properties and has been used for orthopedic and dental implants, for most applications titanium is alloyed with small amounts of aluminium and vanadium, typically 6% and 4% respectively, by weight. This mixture has a solid solubility which varies dramatically with temperature, allowing it to undergo precipitation strengthening. This heat treatment process is carried out after the alloy has been worked into its final shape but before it is put to use, allowing much easier fabrication of a high-strength product. Titanium alloys are generally classified into four main categories: Beta titanium alloys exhibit the BCC allotropic form of titanium (called beta). Elements used in this alloy are one or more of the following other than titanium in varying amounts. These are molybdenum, vanadium, niobium, tantalum, zirconium, manganese, iron, chromium, cobalt, nickel, and copper. The titanium alloys have excellent formability and can be easily welded. Beta titanium is nowadays largely utilized in the orthodontic field and was adopted for orthodontics use in the 1980s. This type of alloy replaced stainless steel for certain uses, as stainless steel had dominated orthodontics since the 1960s. It has strength/modulus of elasticity ratios almost twice those of 18-8 austenitic stainless steel, larger elastic deflections in springs, and reduced force per unit displacement 2.2 times below those of stainless steel appliances. The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal α phase with a c/a ratio of 1.587. At about 890 °C, the titanium undergoes an allotropic transformation to a body-centred cubic β phase which remains stable to the melting temperature. Some alloying elements, called alpha stabilizers, raise the alpha-to-beta transition temperature, while others (beta stabilizers) lower the transition temperature. Aluminium, gallium, germanium, carbon, oxygen and nitrogen are alpha stabilizers. Molybdenum, vanadium, tantalum, niobium, manganese, iron, chromium, cobalt, nickel, copper and silicon are beta stabilizers. Generally, beta-phase titanium is the more ductile phase and alpha-phase is stronger yet less ductile, due to the larger number of slip planes in the bcc structure of the beta-phase in comparison to the hcp alpha-phase. Alpha-beta-phase titanium has a mechanical property which is in between both.