Views: 0 Author: Site Editor Publish Time: 2022-05-06 Origin: Site
Titanium is a new type of metal. The performance of titanium is related to the content of impurities such as carbon, nitrogen, hydrogen and oxygen. The impurity content of the purest titanium iodide is no more than 0.1%, but it has low strength and high plasticity. The properties of 99.5% industrial pure titanium are: density ρ= 4.5g/cm3, melting point 172.5 ℃, thermal conductivity λ= 15.24w / (m.k), tensile strength σ B = 539mpa, elongation δ= 25%, reduction of area ψ= 25%, elastic modulus E = 1.078 × 105Mpa, hardness hb195.
1. High strength
The density of titanium alloy is generally about 4.5g/cm3, which is only 60% of that of steel. The strength of pure titanium is close to that of ordinary steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength/density) of titanium alloy is much higher than that of other metal structural materials. At present, titanium alloy is used in aircraft engine components, skeleton, skin, fasteners and landing gear.
2. High thermal strength
The service temperature of titanium alloy is several times higher than that of aluminum alloy. It can still maintain the required strength at medium temperature. The titanium alloys still have high specific strength in the range of 150 ℃ ~ 500 ℃, while the specific strength of aluminum alloy decreases significantly at 150 ℃. And the working temperature of titanium alloy can reach 500 ℃, while that of aluminum alloy is below 200 ℃.
3. Good corrosion resistance
Titanium alloy works in humid atmosphere and seawater, and its corrosion resistance is much better than that of stainless steel. It has strong resistance to pitting corrosion, acid corrosion and stress corrosion. And titanium alloy has excellent corrosion resistance to alkali, chloride, chlorine organic products, nitric acid, sulfuric acid, etc. However, titanium has poor corrosion resistance to reducing oxygen and chromium salt medium.
4. Good low temperature performance
Titanium alloy can still maintain its mechanical properties at low temperature and ultra-low temperature. Titanium alloys with good low temperature performance and very low interstitial elements, such as TA7, can maintain a certain plasticity at - 253 ℃. Therefore, titanium alloy is also an important low temperature structural material.
5. High chemical activity
Titanium has high chemical activity and has strong chemical reaction with O, N, h, Co, CO2, water vapor and ammonia in the atmosphere. When the carbon content is more than 0.2%, hard tic will be formed in titanium alloy. When the temperature is high, tin hard surface will also be formed by interaction with n. Titanium absorbs oxygen to form a hardened layer with high hardness above 600 ℃. With the increase of hydrogen content, embrittlement layer will also be formed. The depth of hard and brittle surface produced by absorbing gas can reach 0.1 ~ 0.15 mm, and the hardening degree is 20% ~ 30%. The friction between titanium and surface is easy to occur.
6. Small thermal conductivity and elastic modulus
The thermal conductivity of titanium λ= 15.24w/(m.k) is about 1/4 of nickel, 1/5 of iron and 1/14 of aluminum. The thermal conductivity of various titanium alloys is about 50% lower than that of titanium. The elastic modulus of titanium alloy is about 1/2 of that of steel, so its rigidity is poor and easy to deform. It is not suitable to make slender rods and thin-walled parts. During cutting, the resilience of the machined surface is very large, about 2 ~ 3 times that of stainless steel, resulting in severe friction, adhesion and bonding wear on the back surface of the tool. Alloying of titanium titanium alloy is an alloy based on titanium and added with other elements. Titanium has two kinds of homogeneous and heterogeneous crystals: close packed hexagonal structure below 882 ℃ α Titanium, body centered cubic above 882 ℃ β Titanium.
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