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The three main functions of titanium: Functional materials are engineering materials whose properties are primarily physical; in other words, they possess special characteristics in terms of electricity, magnetism, sound, light, heat, etc., or exhibit special functions under the influence of these factors. Research on titanium and titanium alloys has revealed that they possess three special properties with promising applications: First, the memory effect – titanium-nickel alloys exhibit unidirectional, bidirectional, and omnidirectional memory effects at certain ambient temperatures, making them recognized as the best memory alloys. Pipe fittings are used in engineering for the hydraulic systems of fighter jets ； Oil consortium’s pipeline system ； A parabolic mesh antenna with a diameter of 500 mm, made from wires with a diameter of 0.5 mm, is used on aerospace vehicles ； Used in medical engineering for the treatment of snoring ； It is made into screws for use in fracture healing, etc. All the aforementioned applications have achieved significant results. II. Superconducting property: Nickel-titanium alloys exhibit a superconducting property with zero resistance at temperatures below their critical temperature. III. Hydrogen storage capability: Titanium-iron alloys possess the ability to absorb hydrogen, storing large amounts of it safely, and releasing it again under certain conditions. This holds great promise for applications in hydrogen separation, hydrogen purification, hydrogen storage and transportation, as well as in the manufacture of heat pumps and batteries powered by hydrogen. Properties and applications of titanium and titanium alloys. Pure titanium is a silver-white metal with many excellent properties. Titanium has a density of 4.54 g/cm3, which is 43% lighter than steel, and it is slightly heavier than magnesium, the well-known lightweight metal. Its mechanical strength is comparable to that of steel, twice that of aluminum, and five times that of magnesium. Titanium can withstand high temperatures; its melting point is 1942 K, which is nearly 1000 K higher than that of gold, and nearly 500 K higher than that of steel. Titanium is a metal with relatively active chemical properties. When heated, it can react with non-metals such as O2, N2, H2, S, and halogens. However, at room temperature, a very thin and dense oxide protective layer forms on the surface of titanium, which can resist the action of strong acids and even aqua regia, granting it excellent corrosion resistance. Therefore, ordinary metals become pitted in acid, alkali, and salt solutions, while titanium remains intact. Liquid titanium can dissolve almost all metals, allowing it to form alloys with a variety of metals. Titanium added to steel produces titanium steel that is tough and elastic. Titanium forms interstitial compounds or intermetallic compounds with metals such as Al, Sb, Be, Cr, Fe, etc. Aircraft made of titanium alloy can carry more than 100 additional passengers compared to aircraft of the same weight made from other metals. The submarines manufactured are capable of withstanding both seawater corrosion and deep-sea pressure, with a diving depth that is 80% greater than that of stainless-steel submarines. At the same time, titanium is non-magnetic and cannot be detected by mines, giving it excellent counter-surveillance capabilities. Titanium has a \"biocompatible\" nature. In the human body, it can resist the corrosion of secretions, is non-toxic, and is compatible with any sterilization method. Therefore, it is widely used in the manufacture of medical devices, artificial hip joints, knee joints, shoulder joints, thoracic joints, skull components, aortic heart valves, and bone fixation clips. When new muscle fiber rings encircle these “titanium bones,” they begin to support the normal functions of the body. Titanium is widely distributed in the human body; its concentration in a normal human body is no more than 15 mg per 70 kg of body weight, and its functions remain unclear. However, it has been proven that titanium can stimulate phagocytes and enhance immunity. Ten key properties of titanium: 1. Low density and high specific strength. The density of metallic titanium is 4.51 g/cm3, which is higher than that of aluminum but lower than that of steel, copper, and nickel; however, its specific strength ranks first among metals. II. Corrosion resistance: Titanium is a highly reactive metal with a very low equilibrium potential, resulting in a strong thermodynamic tendency to corrode in various media. But in fact, titanium is very stable in many media; it is corrosion-resistant in oxidizing, neutral, and weakly reducing media. This is because titanium has a strong affinity for oxygen; in air or oxygen-containing environments, a dense, strongly adherent, and highly inert oxide layer forms on the surface of titanium, protecting the titanium matrix from corrosion. It can even heal or regenerate quickly even due to mechanical wear. This indicates that titanium is a metal with a strong tendency to passivate. The oxide film of titanium maintains this property at medium temperatures below 315°C. To improve the corrosion resistance of titanium, surface treatment techniques such as oxidation, electroplating, plasma spraying, ion nitriding, ion implantation, and laser treatment have been developed. These techniques enhance the protective properties of titanium’s oxide film, thereby achieving the desired corrosion resistance. To meet the requirements for metal materials in various production processes such as sulfuric acid, hydrochloric acid, methylamine solutions, high-temperature humid chlorine gas, and high-temperature chlorides, a series of corrosion-resistant titanium alloys including titanium-molybdenum, titanium-palladium, and titanium-molybdenum-nickel have been developed. Titanium castings were made from titanium-32 molybdenum alloy; for environments prone to crevice corrosion or pitting, titanium-0.3 molybdenum-0.8 nickel alloy was used, or titanium-0.2 palladium alloy was applied to specific parts of the titanium equipment – all of which yielded excellent results. III. Good heat resistance: The new titanium alloy can be used for extended periods at temperatures of 600°C or higher. IV. Good low-temperature resistance: Low-temperature titanium alloys such as titanium alloy TA7 (Ti-5Al-2.5Sn), TC4 (Ti-6Al-4V), and Ti-2.5Zr-1.5Mo exhibit an increase in strength as the temperature decreases, while their plasticity remains relatively unchanged. It maintains good ductility and toughness at low temperatures of -196 to -253°C, avoiding metal cold brittleness; it is an ideal material for equipment such as low-temperature containers and storage tanks. V. Strong damping performance: When subjected to mechanical or electrical vibrations, titanium exhibits the longest vibration decay time compared to metals such as steel and copper. Taking advantage of this property of titanium, it can be used for tuning forks, vibration elements in medical ultrasonic crushers, and vibration diaphragms in high-end audio speakers. VI. Non-magnetic and non-toxic: Titanium is a non-magnetic metal that does not become magnetized even in strong magnetic fields. It is non-toxic and has good compatibility with human tissues and blood, which is why it is used in the medical field. VII. The tensile strength is close to its yield strength. This property of titanium indicates a high yield ratio (tensile strength/yield strength), suggesting that titanium metal has poor plastic deformation capacity during shaping. Due to the high ratio of titanium’s yield limit to its elastic modulus, it possesses a high springback capacity during shaping. VIII. Good heat transfer performance: Although the thermal conductivity of titanium metal is lower than that of carbon steel and copper, its excellent corrosion resistance allows the wall thickness to be reduced. Moreover, the heat transfer between the surface and steam occurs through droplet condensation, which reduces heat loss; the absence of scaling on the surface also lowers thermal resistance, thereby significantly improving titanium’s heat transfer performance. IX. Low elastic modulus: The elastic modulus of titanium at room temperature is 106.4 GMPa, which is 57% of that of steel. X. Absorption properties: Titanium is a metal with highly reactive chemical properties; it can react with many elements and compounds at high temperatures. Titanium absorption of gases mainly refers to reactions with carbon, hydrogen, nitrogen, and oxygen at high temperatures.