Titanium and its properties

Titanium is a metallic chemical element, chemical symbol Ti, atomic number 22, belongs to refractory rare non-ferrous metals.

Titanium properties and the contained carbon, hydrogen, oxygen and other impurities, the purest titanium iodide impurity content of no more than 0.1%, but its strength is low, high plasticity. 99.5% industrial pure titanium properties are: density P = 4.5g/cm3, melting point of 1800 ° C, thermal conductivity λ = 15.24W / (M.K), tensile strength σ b = 539MPa, elongation: δ = 25%, sectional elongation:δ =25%, section shrinkageψ=25%, elastic touch E=1.078×105MPa, hardness HB195.

Titanium is a silver-white transition metal, characterized by low density, high melting point, high specific strength, corrosion resistance, high and low temperature performance, non-magnetic, non-toxic, biocompatible. Among them, the high strength performance is particularly prominent, high strength titanium alloy strength and high strength steel, but the density is almost half of the small. In addition, titanium and alloys also have shape memory, superconductivity and hydrogen storage and other characteristics.

Titanium properties

High strength: 1.3 times that of aluminum alloys, 1.6 times that of magnesium alloys, 3.5 times that of stainless steel, the champion of metal materials. Titanium alloy density is generally around 4.5g/cm3, only 60% of steel, the strength of pure titanium is close to the strength of ordinary steel, some high-strength titanium alloy exceeds the strength of many alloy structural steel, so titanium alloys than the strength (strength / density) is much greater than other metal structural materials, can be made of unit of high strength, toughness, lightweight parts and components, in the aircraft engine structural parts, skeleton, skin, In the aircraft engine structure, skeleton, skin, fasteners and landing gear, etc. are used titanium alloy.

High thermal strength: the use of temperature than the aluminum alloy a few hundred degrees higher, in the medium temperature can still maintain the required strength, can be in the 450-500 ° C temperature of long-term work.

Good corrosion resistance: resistant to acid, alkali and atmospheric corrosion, with particularly strong resistance to pitting and stress corrosion. Titanium alloy in the humid atmosphere and seawater media work, other corrosion resistance is far better than stainless steel; pitting, acid corrosion, stress corrosion resistance is particularly strong, alkali, chloride, chlorine organic items, nitric acid, sulfuric acid, etc. have excellent corrosion resistance, but titanium has a reducing oxygen and chromium salt media corrosion resistance is poor.

Good low-temperature performance: titanium alloy TA7 with very low interstitial elements can maintain a certain degree of plasticity at -253℃. Titanium alloy at low and ultra-low temperatures, can still maintain its mechanical properties, low-temperature performance is good, the interstitial elements of the very low titanium alloy, such as TA7, in -253 ° C can also maintain a certain degree of plasticity, so the titanium alloy industry is an important low-temperature structural materials.

Chemical activity: high chemical activity at high temperatures, easily with hydrogen, oxygen and other gaseous impurities in the air chemical reaction to generate a hardened layer. Titanium's chemical activity is large, and the atmosphere O, N, H, CO, CO2, water vapor, ammonia, etc. to produce a strong chemical reaction. When the carbon content is greater than 0.2%, hard TiC will be formed in the titanium alloy; at higher temperatures, a TiN hard surface layer will be formed by acting with N. Above 600°C, titanium absorbs oxygen to form a hardened layer with high hardness; the rise in hydrogen content will also form an embrittled layer. The depth of the hard and brittle surface layer resulting from the absorption of gas can be up to 0.1-0.15 mm, with a hardening degree of 20-30%. Titanium's chemical affinity is also large, easy with the adhesion phenomenon produced by the friction surface.

Thermal conductivity is small, elastic touch small: titanium's thermal conductivity λ = 15.2W / (M, K) is about 1/4 of nickel, iron 5/1, aluminum 1/14, and a variety of titanium alloys than titanium's coefficient of thermal conductivity of the thermal conductivity of the titanium alloy about 50% down, titanium alloys, elastic touch about 1/2 of the steel, so its rigidity is poor, easy to deform, not suitable for making long thin rods and thin-walled parts, cutting, machining the surface of the rebound is large, about 2-3 times, causing the surface to adhere to the friction surface. Stainless steel 2-3 times, resulting in intense friction, adhesion, bonding wear of the tool rear blade surface.