The finished products of niobium and niobium alloy materials and their processing and preparation processes need to be annealed and heat treated. The heat treatment methods include homogenization heat treatment, stress relief heat treatment, recrystallization heat treatment and mechanical heat treatment.
-Homogenization heat treatment. The homogenization heat treatment is to eliminate defects such as metastable phases and component segregation in the ingot by atomic diffusion, and to make the structure uniform and stable.
The homogenization temperature of the niobium ingot is 1800~2000 ℃, the vacuum degree is 10-2~10-3Pa, and the holding time is 5-10h.
-Stress-relief heat treatment. The purpose of stress-relief annealing is to eliminate or reduce the internal stress of the material and improve the mechanical and technological performance of the material. Therefore, at a given temperature, the stress and strain energy can be eliminated quickly.
-Recrystallization heat treatment. The recrystallization heat treatment can eliminate the processed structure and restore the properties of the material to the state before deformation. Through the interaction of deformation and recrystallization annealing, component segregation can be eliminated, the grains can be broken, the structure can be uniform, and the plate can be prevented from delaminating, coarse grains and brittle cracking. So as to improve material yield and performance.
-Mechanical heat treatment. The mechanical heat treatment of the niobium alloy is obtained by the “solution treatment → cold deformation → aging” treatment.
Precipitation strengthening to improve the overall performance of the alloy. The mechanical heat treatment process of Nb-10W-1Zr-0.1C alloy is 1650 ℃, 10min → 20%~30% cold deformation → 1420 ℃, 1h.
During the mechanical heat treatment, the solid solution and aging temperature and time and the amount of cold deformation have a great impact on the material properties. These parameters must be reasonably selected and strictly controlled to make the alloy structure uniform, especially the uniform dispersion of the precipitation phase. The alloy has both good high-temperature strength and appropriate room-temperature plasticity, formability, and high-temperature thermal stability.