The first high-temperature titanium alloy successfully developed worldwide is Ti-6Al-4V, with a service temperature of 300-350℃. Subsequently, alloys such as IMI550 and BT3-1 with a service temperature of 400℃ and IMI679, IMI685, Ti-6246, Ti-6242 with a service temperature of 450~500℃ were developed. New high-temperature titanium alloys successfully used in aircraft engines include IMI829 and IMI834 alloys in the UK; Ti-1100 alloy in the United States; BT18Y and BT36 alloys in Russia. In recent years, foreign countries have made use of rapid solidification/powder metallurgy technology and fiber or particle-reinforced composite materials to develop titanium alloys as the development direction of high-temperature titanium alloys, so that the service temperature of titanium alloys can be increased to above 650℃. McDonnell Douglas of the United States has successfully developed a high-purity, high-density titanium alloy using rapid solidification/powder metallurgy technology. Its strength at 760°C is equivalent to the strength of titanium alloys currently used at room temperature.
Titanium alloys based on titanium-aluminum compounds
Compared with general titanium alloys, the advantages of titanium-aluminum compounds based on sodium Ti3Al (α2) and TiAl (γ) intermetallic compounds are good high-temperature performance (the operating temperature is 816 and 982°C respectively), strong oxidation resistance, good creep resistance, and light weight (density is only 1/2 of nickel-based high-temperature alloys). These advantages make it a competitive material for future aero-engines and aircraft structural parts. At present, two Ti3Al-based titanium alloys Ti-21Nb-14Al and Ti-24Al-14Nb-#v-0.5Mo have begun mass production in the United States. Other Ti3Al-based titanium alloys developed in recent years include Ti-24Al-11Nb, Ti25Al-17Nb-1Mo, and Ti-25Al-10Nb-3V-1Mo. The composition range of TiAl (γ)-based titanium alloys is TAl-(1-10)M (at.%), where M is at least one of v, Cr, Mn, Nb, Mn, Mo and W. Recently, TiAl3-based titanium alloys have begun to attract attention, such as Ti-65Al-10Ni alloy.
High-strength and high-toughness β-type titanium alloy
β-type titanium alloy was first developed by Crucible in the United States in the mid-1950s as B120VCA alloy (Ti-13v-11Cr-3Al). β-type titanium alloy has good hot and cold processing properties, is easy to forge, can be rolled and welded, and can obtain higher mechanical properties, good environmental resistance, and a good combination of strength and fracture toughness through solid solution-aging treatment. The representative new high-strength and high-toughness β-type titanium alloys are as follows: Ti1023 (Ti-10v-2Fe-#al), which has the same performance as the 30CrMnSiA high-strength structural steel commonly used in aircraft structural parts and has excellent forging performance; Ti153 (Ti-15V-3Cr-3Al-3Sn), which has better cold working performance than industrial pure titanium, and the room temperature tensile strength after aging can reach more than 1000MPa; β21S (Ti-15Mo-3Al-2.7Nb-0.2Si), which is a new type of oxidation-resistant, ultra-high-strength titanium alloy developed by the Timet division of the American titanium metal company, has good Good oxidation resistance, excellent hot and cold processing performance, can be made into foil with a thickness of 0.064mm; SP-700 (Ti-4.5Al-3V-2Mo-2Fe) titanium alloy successfully developed by Nippon Steel Tube Co., Ltd. (NKK) has high strength, superplastic elongation of up to 2000%, and superplastic forming temperature is 140℃ lower than Ti-6Al-4V, which can replace Ti-6Al-4V alloy to manufacture various aerospace components using superplastic forming-diffusion bonding (SPF/DB) technology; BT-22 (TI-5v-5Mo-1Cr-5Al) developed by Russia has a tensile strength of more than 1105MPA.
Flame-retardant titanium alloy
Conventional titanium alloys tend to burn alkanes under certain conditions, which greatly limits their application. In response to this situation, various countries have launched research on flame-retardant titanium alloys and achieved certain breakthroughs. Alloy C (also known as T) developed by Qiang State has a nominal composition of 50Ti-35v-15Cr (mass fraction). It is a flame-retardant titanium alloy that is insensitive to continuous combustion and has been used in F119 engines. BTT-1 and BTT-3 are flame-retardant titanium alloys developed by Russia. Both are Ti-Cu-Al alloys with very good thermal deformation process performance and can be used to make complex parts.
Medical titanium alloys
Titanium is non-toxic, light, high in strength, and has excellent biocompatibility. It is an ideal medical metal material and can be used as an implant for the human body. At present, Ti-6Al-4v is still widely used in the medical field. ELI alloy. However, the latter will precipitate a very small amount of vanadium and aluminum ions, which reduces its cell adaptability and may cause harm to the human body. This issue has long attracted widespread attention in the medical community. As early as the mid-1980s, the United States began to develop aluminum-free, vanadium-free, biocompatible titanium alloys for use in orthopedics. Japan, the United Kingdom, and other countries have also done a lot of research in this area and have made some new progress. For example, Japan has developed a series of α+β titanium alloys with excellent biocompatibility, including Ti-15Zr-4Nb_4ta-0.2Pd, Ti-15Zr-4Nb-aTa-0.2Pd-0.20~0.05N, Ti-15Sn-4Nb-2Ta-0.2Pd and Ti-15Sn-4nb-2Ta-0.2Pd-0.20. The corrosion strength, fatigue strength, and corrosion resistance of these alloys are better than those of Ti-6Al-4v ELI. Compared with α+β titanium alloy, β titanium alloy has higher strength, better cutting performance, and toughness, and is more suitable for implantation in the human body. In the United States, five β titanium alloys have been recommended for the medical field, namely TMZFTM (TI-12Mo-^Zr-2Fe), Ti-13Nb-13Zr, Timetal 21SRx (TI-15Mo-2.5Nb-0.2Si), Tiadyne 1610 (Ti-16Nb-9.5Hf) and Ti-15Mo. It is estimated that soon, this type of titanium alloy with high strength, low elastic modulus, excellent formability, and corrosion resistance is likely to replace the Ti-6Al-4V ELI alloy currently widely used in the medical field.
