The development of high pulse thrust-weight ratio engines for advanced aerospace rocket technology products requires the use of titanium alloys with higher low temperature strength and plasticity. For this reason, the Metal Research Institute of the Russian "Composite Materials" joint-stock company is carrying out the process determination cycle of BT6c alloy for this project. This alloy is used to produce φ600mm die forgings with operating temperatures up to -200℃, plates for accumulators, bearing brackets and billets for pipe joints. At present, we are exploring ways to reduce the working temperature of the alloy to a 253'C, one of which is to obtain parts by particle metallurgy. This process can ensure that all parts of the billet have uniform fine crystal structure, and make the whole billet performance isotropic. Dense blank was prepared from BT6c alloy particles after hot isostatic pressing in α+β zone + one-stage roasting. The strength was 100MPa higher than that of BT5-1KT alloy, and the fatigue performance was higher.
The most widely used titanium alloys in space rockets are two-phase alloys BT6c, BTl4, BT3-1, BT23, BTl6, BT9 (BT8), which are mainly used in heat treatment strengthening states. Annealing BT6c alloy can be used in accumulators, but the alloy is mostly used in the heat treatment strengthening state σb = 1050MPa - 1100MPa. Similar applications include BTl4 alloys σb = 1100MPa ~ 1150MPa. The annealed BTl4 alloy σb≥900MPa can be used as a tubular beam with a diameter of 80mm to 120mm, and is also used in the manufacture of fasteners operating at -196 ° C.
In recent years, the isothermal stamping process of BT23 alloy with outer diameter up to 350mm hemispheres has been developed. Compared with the overall hot stamping, this process can reduce the mass of the stamping part from 36kg to 8.5kg, the wall thickness from 22mm to 10mm, and the metal utilization rate from 0.15 to 0.64. Widely used in space rockets are BT5, BT20 alloy castings, the mass of up to 100kg. A cast titanium alloy (Ti-6A1-20Zr-2Mo) with a strength of 1050MPa-1100mpa was developed and tested, and a cast weighing 200kg was obtained. Hot isostatic pressing of castings was developed. After processing, the yield of castings is increased from 70% to 92%, the elongation of castings is increased by 30%, the impact toughness is increased by 50% ~ 150%, and the fatigue strength is increased by 50%. Titanium-nickel alloys with "shape memory" effects are also used. TH1 alloy is used as a self-opening antenna, push rod, contactor, and shock absorber for aerospace systems. The THlk low-temperature alloy with a shape recovery temperature of 80 ° C can be used to manufacture connectors for pipes and equipment in various hydraulic systems and power systems.
At present, Ti-Al intermetallic compound based alloys are being studied. The alloy has a unique combination of properties, high thermal strength and elastic modulus, and low density, making these alloys the most promising alloys for the new generation of space rockets. "Composite Materials" research and production joint company is developing a comprehensive process equipment for making billets with these materials, including melting equipment, particle production equipment, isothermal deformation equipment, etc.