At present, the turbine inlet temperature of the advanced aircraft engine is greater than 1350℃, the density of the nickel-based alloy used now is 8.0g/cm3-9.2g/cm3, the melting point is 1300℃-1350℃, and the maximum working temperature is less than 1200℃, so special processing and cooling technology must be used to use; Its application in new and advanced aerospace spacecraft is limited due to its heavy ratio and limited operating temperature. By reducing material density or mass, it can increase payload, extend range, and reduce fuel consumption, which is an important idea in aerospace design. The new Nb-Ti-Al low density niobium alloy is an important candidate material to meet these objective requirements. Because of its low density, easy processing and good oxidation resistance, it has become a new class of materials that attract attention, which is suitable for important high-temperature parts in aerospace engineering. Due to the addition of different alloying elements, this series of alloys can be divided into Nb-Ti-Al elastic alloys, Nb-Ti-Al-V-Zr alloys and Nb-Ti-Al-Cr-Hf-W-Mo alloys.
The preparation of niobium alloy plate and bar is usually first made of ingots by electron beam melting or plasma arc melting, then by forging or extrusion processing to open the billet, refine the grain structure, improve the plasticity of the alloy, and finally by forging or rolling method to prepare the blank into the required specifications of plate and bar. Northwest Non-Ferrous Metal Research Institute recently successfully prepared the low-density niobium alloy sheet using a similar scheme and published in the literature, and its cold and hot processing performance is excellent. However, the niobium alloy plate prepared by the process route has a low yield, about 20% to 30%, and because of the alloy's high hardness and high room temperature strength, the turning process is difficult, and the stress relief annealing over 1000℃ can not significantly soften the material, which is not conducive to the recycling of scraps, and it is difficult to reduce the cost of alloy preparation. Therefore, it is urgent to develop a simple and economical method for preparing sheet metal.
In addition to electron beam melting or plasma arc melting, hot isostatic pressing is also one of the important methods to prepare refractory alloy blanks. Refractory metal powder can also be prepared into slabs with corresponding compositions under high temperature and high pressure. The coated niobium alloy powder is kept warm for a long time under high temperature and pressure by hot isostatic press. The density of the alloy is improved by sintering, molding and recrystallization at high temperature. The force of the hot isostatic press on the billet at high temperature is greater than the yield strength of the niobium alloy at the corresponding temperature, so as to ensure that the niobium alloy powder is fully dense sintering and plastic deformation.
