Advantages Titanium alloy
Time: 2013-08-01 11:20
High thermal strength
Temperature several hundred degrees higher than aluminum, at moderate temperatures can still maintain the required strength, the temperature of 450 ~ 500 ℃ long-term work at these two types of alloy 150 ℃ ~ 500 ℃ range is still very high specific strength, and aluminum at 150 ℃ than intensity decreased significantly. Titanium operating temperature up to 500 ℃, aluminum is below 200 ℃.
Good corrosion resistance
Titanium in the humid atmosphere and seawater media work, which is far superior corrosion resistance of stainless steel; the pitting, etching, particularly strong resistance to stress corrosion; alkali, chloride, chlorine, organic materials, nitric acid, sulfuric acid etc. have excellent corrosion resistance. However, with the reduction of titanium oxide and chromium salts medium, poor corrosion resistance.
Good low temperature performance
Titanium alloys at low and ultra-low temperatures, can still maintain its mechanical properties. Low temperature performance, low interstitial elements titanium, as TA7, at -253 ℃ and can keep a certain plasticity. Therefore, titanium is also an important temperature structural materials.
Large chemical activity
Large chemical activity of titanium, with atmospheric O, N, H, CO, CO2, water vapor, ammonia, etc. have a strong chemical reaction. Carbon content greater than 0.2%, the titanium alloy is formed in the hard TiC; temperature is higher, the effect will be the formation of N TiN
Hard surface; at above 600 ℃, high hardness titanium absorbs oxygen to form a hardened layer; hydrogen content increased, will form brittle layer. Gas absorption resulting brittle skin depth of up to 0.1 ~ 0.15 mm, hardening degree of 20% to 30%. The chemical affinity of titanium is large, easy to sticking and friction surface.
Thermal conductivity, the elastic modulus is small
The thermal conductivity of titanium λ = 15.24W / (mK) of nickel about 1/4, Fe 1/5, of aluminum 1/14, and various titanium titanium thermal conductivity than the thermal conductivity of about 50%. Titanium steel elastic modulus of about 1/2, so the difference in rigidity, deformation, not making the elongated rod and thin-walled parts, the machined surface when cutting a large amount of springback, about 2-3 stainless steel times, resulting in a sharp tool flank friction, adhesion, adhesive wear.
Heat treatment
Annealing heat treatment methods are used, solution and aging treatment. Annealing is to eliminate stress, improve plasticity and organizational stability in order to obtain a better overall performance. Typically α alloys and (α + β) alloy annealing temperature selected in the (α + β) ─ → β phase transition point 120 ~ 200 ℃; solution and aging treatment from the high temperature zone rapid cooling to obtain martensite α 'phase and metastable The β phase temperature region and in the heat decomposition of these metastable phases, to obtain compound α phase or the dispersed second phase particles, to achieve the purpose of strengthening the alloy. Usually (α + β) alloy quenched in (α + β) ─ → β phase transition point 40 ~ 100 ℃ for metastable β alloys quenched in (α + β) ─ → β phase transition point above 40 ~ 80 ℃ for. Aging treatment temperature is generally 450 ~ 550 ℃. Summary, titanium heat treatment process can be summarized as follows: (1) stress relief annealing: the aim is to eliminate or reduce the processing residual stresses generated in the process. In some corrosive environment to prevent chemical attack and reduce distortion. (2) fully annealed: The aim is to get a good toughness, improve processing performance, is conducive to further processing and to improve the size and organizational stability. (3) solution treatment and aging: the aim is to improve its strength, α β titanium alloy and stability can not be strengthening heat treatment, annealing only in production. α + β titanium alloys containing a small amount of α-phase metastable β titanium alloy by solid solution treatment and aging of the alloy further strengthened. Furthermore, in order to meet the special requirements of the workpiece, the industry also uses double annealing, isothermal annealing, β heat treatment, deformation of metal heat treatment and heat treatment.
Edit this paragraph cutting
Cutting Features
Only trace cutting, the cut chips have a small ignition combustion phenomena. To avoid fire hazard, in addition to a large number of cutting fluid pouring outside, but also to prevent the accumulation of chips in the machine tool to be replaced immediately with a blunt, or lower cutting speed, increase the amount of feed to increase the chip thickness. If once the fire should be used talcum powder, limestone powder, dry sand and other fire fighting equipment for fighting, prohibited the use of carbon tetrachloride, carbon dioxide fire extinguisher, can not watering, because water can accelerate the burning, and even lead to a hydrogen explosion.
Titanium, aluminum, titanium compounds based
Compared with the general titanium, titanium-based compound is sodium aluminum Ti3Al (α2) and TiAl (γ) intermetallics biggest advantage is high performance (maximum use temperatures of 816 and 982 ℃), anti-oxidation, anti- good creep resistance and light weight (density of only nickel-base superalloy 1/2), these advantages make it become the future aircraft engines and aircraft structural parts of the most competitive materials [26]. Currently, there are two Ti3Al-based titanium alloy Ti-21Nb-14Al and Ti-24Al-14Nb-# v-0.5Mo start mass production in the United States. Other recent development has Ti3Al-based titanium Ti-24Al-11Nb, Ti25Al-17Nb-1Mo and Ti-25Al-10Nb-3V-1Mo etc. [29]. TiAl (γ) of the titanium-based composition ranging concern Ti-(46-52) Al-(1-10) M (at.%), where M is v, Cr, Mn, Nb, Mn, Mo and W, at least one element. Recently, TiAl3 based titanium began to attract attention, such as Ti-65Al-10Ni alloy [1].
Β-type titanium alloy high strength and high toughness
β-type titanium alloy was first used by the mid-1950s, the company developed the American Crucible B120VCA alloy (Ti-13v-11Cr-3Al). β-type titanium alloy having excellent cold workability, easy to forging, can be rolled, welded, through the solution - aging treatment to get high mechanical properties, good environmental resistance and good strength and fracture toughness with. New high strength and high toughness β-type titanium alloy most representative are the following [26,30]: Ti1023 (Ti-10v-2Fe-# al), and aircraft structural components of the alloy commonly used in high-strength structural steel properties 30CrMnSiA rather, forging has excellent properties; Ti153 (Ti-15V-3Cr-3Al-3Sn), the alloy cold better performance than the commercially pure titanium, up to room temperature tensile strength after aging than 1000MPa; β21S (Ti-15Mo- 3Al-2.7Nb-0.2Si), the titanium alloy by the U.S. company developed a new division Timet antioxidant, high strength titanium alloy with good oxidation resistance, good hot workability, the thickness can be made The foil is 0.064mm; NKK Corporation (NKK) the successful development of SP-700 (Ti-4.5Al-3V-2Mo-2Fe) titanium alloy, the alloy high strength, superplastic elongation up to 2000%, and superplastic forming temperature than the Ti-6Al-4V low 140 ℃, can be replaced by Ti-6Al-4V alloy superplastic forming - diffusion bonding (SPF / DB) technology to produce a variety of aerospace components; Russia developed the BT-22 (TI- 5v-5Mo-1Cr-5Al), the tensile strength of up to more than 1105MPA
Resistant titanium alloy
Conventional titanium alloy under certain conditions alkyl burning tendency, which largely limits its application. To address this situation, countries have launched a study on the resistant titanium alloy and made some breakthroughs. Qiang States developed the Alloy c (also known as Ti-1720), nominal composition of 50Ti-35v-15Cr (mass fraction), is a kind of sustained combustion insensitive resistant titanium alloy has been used in the F119. BTT-1 and BTT-3 for the Russian-developed resistant titanium alloy, both Ti-Cu-Al alloys with very good thermal deformation process performance, made available its complex parts [26].
Compounds based alloy
Compared with the general titanium, titanium-based compound is sodium aluminum Ti3Al (α2) and TiAl (γ) intermetallics biggest advantage is high performance (maximum use temperatures of 816 and 982 ℃), anti-oxidation, anti- good creep resistance and light weight (density of only nickel-base superalloy 1/2), these advantages make it become the future aircraft engines and aircraft structural parts of the most competitive materials [26].
Currently, there are two Ti3Al-based titanium alloy Ti-21Nb-14Al and Ti-24Al-14Nb-# v-0.5Mo start mass production in the United States. Other recent development has Ti3Al-based titanium Ti-24Al-11Nb, Ti25Al-17Nb-1Mo and Ti-25Al-10Nb-3V-1Mo etc. [29]. TiAl (γ) of the titanium-based composition ranging concern Ti-(46-52) Al-(1-10) M (at.%), where M is v, Cr, Mn, Nb, Mn, Mo and W, at least one element. Recently, TiAl3 based titanium began to attract attention, such as Ti-65Al-10Ni alloy [1].
