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Metal niobium has good toughness, ductility and low-temperature processing properties, but it has strong chemical activity and high melting point. Its properties are very sensitive to the content of impurities. Only a few hundred parts per million of oxygen, hydrogen or carbon can make niobium become Hard and brittle. The usual melting and casting methods cannot produce high-purity metal ingots and niobium alloy ingots. Vacuum high-temperature sintering powder metallurgy and electron beam furnace (EB), vacuum consumable electric arc furnace (VAR) vacuum melting methods are suitable for producing high-purity metals and niobium alloy ingots. An ideal common method for niobium and niobium alloy ingots.

Among refractory metals, niobium has a low density (8.6 g/cm’) and good room temperature plasticity and processing properties. Due to these advantages, the design, processing, manufacturing and application of niobium alloys have always attracted the attention of high-temperature materials science and engineering scientists and aerospace science and engineering designers. Since 1950, advanced countries in the world have invested a lot of manpower, material resources and funds in the research and development of niobium and niobium alloy material science and engineering, and have successfully developed a series of various niobium alloys that can be used in 600-1 600°C environments. Niobium alloys are generally classified according to their usage characteristics and strength. Among them, there are five categories of structural niobium alloys: ① low-strength niobium alloy; ② medium-strength niobium alloy; ③ high-strength niobium alloy; ④ low-density niobium alloy; ⑤ high-strength niobium alloy reinforced by interstitial compounds. The alloys classified according to their usage characteristics include: ① elastic niobium alloy; ② superconducting niobium alloy; ③ anti-oxidation niobium alloy; ④ constant expansion niobium alloy, etc.
The following introduces the five types of structural niobium alloys.

Low-strength niobium alloy: Using niobium as the base metal, adding Group IVB Ti, Zr, Hf and other elements to form a solid solution strengthened alloy, such as Nb-1Zr alloy, Nb-10Hf-1Ti-0.7Zr alloy, which has Strength σb = 320 ~ 420 MPa, elongation 8 = 20% ~ 40%, good welding performance, under 0.37 ~ 0.47T temperature and vacuum conditions, after 1000 h aging treatment, its plastic-brittle transition temperature (DBTT ) is still below room temperature. This type of alloy can be used in turbine pumps and liquid alkali metal delivery pipes for space nuclear power generation equipment, as well as attitude control of spacecraft, satellites, missiles and thrust chamber body extensions of mobile engines.

Medium strength niobium alloy: using niobium as the base metal, adding no more than 10% of tungsten, molybdenum, tantalum, vanadium, titanium, zirconium, hafnium and other metal elements and a small amount of carbon element to form solid solution strengthening and a small amount of ZrO2 ( Niobium alloys that combine orthorhombic structure) with (Nb, Zr)c precipitation strengthening, such as Nb752 (Nb – 10W -2.5Zr), D43 (Nb – 10W-1Zr-0.1C), Sab291 (Nb-10W-10Ta) , D31 (Nb-10W-10Ti), B33 (Nb-5W), C-129Y (Nb-10W-10H-0.1Y) and other alloys. At room temperature, the strength of these alloys is σb = 450 ~ 600 MPa, elongation = 20% ~ 30%, and they still have quite high strength between 1000 ~ 1400℃. Since this type of alloy is sensitive to interstitial elements such as hydrogen, oxygen, and nitrogen, its DBTT is relatively high, and the DBTT in the welded state is generally above room temperature. Therefore, during production and use, hydrogen, oxygen, and nitrogen pollution must be strictly controlled, and the oxygen and nitrogen content must be controlled below 80×10~6. This type of alloy is suitable for manufacturing riveted and fastened components, such as skins, bolts, nuts, etc.

High-strength niobium alloy: using niobium as the base metal, adding a large amount of tungsten, molybdenum, tantalum, titanium, zirconium and other metal elements and a small amount of carbon and other elements to form a highly solid solution strengthening and (Nb, Zr)C precipitation strengthening phase Combined niobium alloys, such as AS-30 (Nb-15W- 5M-STi-1Zr), FS-85 (Nb-28Ta-10W -1Zr), Su31 (Nb-17W-3.5Hf-0.12C) and other alloys. This type of alloy has quite high tensile strength, creep strength and fatigue strength in the range of 1300 ~ 1600℃. For example, the stress rupture strength of Su31 alloy at 1430℃ for 10 h and 100 h is 84 MPa and 56 MPa respectively. The creep strengths are 63 MPa and 28 MPa respectively. This type of alloy is suitable for the manufacture of high-temperature components.

With the progress and development of niobium alloy materials and aerospace science and engineering, the enhanced design, production and manufacturing processing of niobium alloys have entered a new stage, and a batch of new niobium alloys with application prospects have been successfully developed: low density Niobium alloy, a high strength alloy reinforced with interstitial compounds.

Low-density niobium alloy: Niobium alloys have two common weaknesses. First, the density of the alloy is higher than that of silver. Second, the high-temperature oxidation resistance of the alloy is very poor. When used at high temperatures, an anti-oxidation coating must be applied to the surface of the alloy. Moreover, when the anti-oxidation coating on the surface is destroyed, the alloy matrix will also be destroyed immediately, which is a “catastrophic” failure. Therefore, it is objectively required to have a new energy alloy that can have both low density and high strength under usage conditions, as well as good anti-oxidation properties, so as to meet the needs of advanced aircraft, spaceships, missiles, etc. to reduce their own weight and increase their size. payload, increase range, and save fuel. The development of this new type of Cui alloy is of great significance to the development of future interstellar transportation and the establishment of large-scale space pilot factories.

Research results show that using niobium as the base metal, adding a large amount of tungsten, molybdenum, tantalum, vanadium, titanium, zirconium, chromium, tin and carbon and other elements will form a high degree of solid solution strengthening and the precipitation of TiAl, (Nb, Zr)C and other compounds Strengthened niobium alloys, such as Nb-45Ti-15AI, Nb-45Ti-5Hf-5V-0.5Zr-0.1C (molar fraction), Nb-38Ti-5Hf-5V-5Cr-2Sn-0.1C (molar fraction) and other alloys. The density of these alloys at room temperature is 5.9~6.9 g/crm, which is 70%~80% of the density of niobium. Without an anti-oxidation coating on the surface of the alloy, it can be used in an atmospheric environment of 550~800℃ without being damaged. Oxidation, under the condition of adding an oxidation coating. It can be used in an atmospheric environment of 800-1300℃, and when the surface coating is damaged, the alloy matrix will not be burned through and destroyed immediately.

High-strength niobium alloy reinforced with interstitial compounds: Niobium alloys can no longer meet the requirements of today’s aerospace engineering technology. It has become the goal of materials scientists to develop an alloy that not only maintains the plasticity of existing high-strength niobium alloys but also has higher strength. Important tasks. Based on the study and analysis of the Nb-M x (M-TiZr, H, A new generation of highly precipitation-strengthened and dispersion-strengthened yue alloys, the concentration ranges of the two sets of alloys are listed in Table 10.4-9. These alloys have high strength in the range of 1100 ~ 1400℃, such as Nb -0.3% ZO. (Mass fraction) The room temperature strength of the alloy in the recrystallized state at 1300°C/1 h is o, = 300 MPa, and the elongation is o = 20%; the strength at 1200°C = 120 MPa, and the elongation is = 36%. Another example is the Nb-4% ZrN (volume fraction) alloy, in the quenched and aged state, its room temperature strength o = 850 MPa, elongation = 16%, and the strength at 1200°C o, = 480 MPa; this alloy can also Adding 10% Mo (mass fraction) further solid solution strengthening, its room temperature strength = 950 MPa, elongation. = 8%, strength at 1200°C o. =550 MPa, elongation o= 10%. At the same time, this type of alloy has good processing plasticity in alloy ingots at room temperature and at temperatures above 800°C. Therefore, it is very meaningful to pay attention to the research and development of this type of alloy.