Heat treatment of niobium alloy

Niobium alloy materials need to be heat-treated in vacuum annealing furnace in the process of production and processing as well as the final product. According to different heat treatment processes and heat treatment methods, it can be divided into four heat treatment systems: homogenization heat treatment, stress relief heat treatment, recrystallization heat treatment and mechanical heat treatment. The homogenization heat treatment mainly uses atomic diffusion to eliminate the metastable phase and composition segregation phenomenon in niobium alloy materials, and obtains the niobium alloy materials with uniform structure and stable performance. The homogenization heat treatment process is usually used in the ingot of niobium alloy. The heat treatment temperature is generally set to 1800~2000℃ according to the size and weight of the ingot of niobium alloy, and the holding time varies from 5h to 10h. Stress relief heat treatment is mainly used to eliminate or reduce the internal stress of niobium alloy materials, generally at a certain temperature, the stress will be quickly eliminated, reduce the strain energy. The usual niobium alloy stress relief return temperature is about 1000℃, insulation for 1h, several special niobium alloy materials (such as D-43,F-48, etc.) temperature will increase to 1200℃, insulation for 1h. Recrystallization is also called the intermediate annealing heat treatment, can alloy grain group after cold deformation and broken, work hardening, plasticity, ductility, and then will have a recrystallization heat treatment niobium alloy materials and deform grain back into uniform equiaxed grain and eliminate composition segregation and processing organization, make organization even, to prevent coarse grain and embrittlement. The prerequisite of recrystallization heat treatment is cold working and a certain amount of cold plastic deformation. The recrystallization temperature of niobium alloys is usually 900~1300℃, and the recrystallization heat treatment temperature of some niobium alloys may reach more than 1500℃. The mechanical heat treatment of niobium alloy is mainly treated by solution → cold deformation → aging to strengthen the precipitation and improve the comprehensive properties of the alloy. The solid solution, aging temperature and time, and the amount of cold processing have great influence on the properties of niobium alloy materials, especially the precipitation phase dispersion uniform distribution. For example, the mechanical heat treatment process of Nb-10W-1Zr-0.1C alloy is 1650℃, holding for 10 minutes, and then 20~30% of the cold processing capacity, and finally 1420℃ for 1 hour, such a heat treatment process can improve the high temperature strength and thermal stability of the alloy, and maintain the plasticity at room temperature.