What is the principle and purpose of annealing? What are the classifications of annealing technology? -Kehua

In terms of metal processing, factories will use heat treatment processes, of which the more common process is annealing. What is the principle and purpose of annealing? What are the classifications of annealing technology? Solving these problems allows us to better understand the knowledge of heat treatment process. Annealing principle Annealing is a metal heat treatment process, which refers to slowly heating the metal to a certain temperature, keeping it for a sufficient time, and then cooling it at a suitable speed. To be precise, annealing is a heat treatment process for materials, including metallic materials and non-metallic materials. Moreover, the purpose of annealing of new materials is similar to that of traditional metal annealing. The purpose of annealing (1) Reduce hardness and improve machinability. (2) Reduce residual stress, stabilize size, reduce deformation and crack tendency; (3) Refine grain, adjust structure, and eliminate structure defects. (4) Uniform material organization and composition, improve material properties or prepare organization for subsequent heat treatment. Annealing principle Maximum heating temperature One of the most important process parameters for annealing is the maximum heating temperature (annealing temperature). The choice of annealing heating temperature for most alloys is based on the phase diagram of the alloy system. The annealing temperature of various steels (including carbon steel and alloy steel), depending on the specific annealing purpose, is a certain temperature above Ac3 and above or below Ac1 for each steel type. The annealing temperature of various non-ferrous alloys is a certain temperature below the solidus temperature of each alloy, above or below the solidus temperature. Classification of annealing technology Semiconductor annealing Semiconductor chips need to be annealed after ion implantation. Because when impurity ions are implanted into the semiconductor, the high-energy incident ions will collide with the atoms on the semiconductor lattice, causing some lattice atoms to be displaced, resulting in a large number of vacancies, which will make the arrangement of atoms in the implanted area chaotic or become It is an amorphous region, so after ion implantation, the semiconductor must be annealed at a certain temperature to restore the crystal structure and eliminate defects. At the same time, annealing also has the function of activating the donor and acceptor impurities, that is, some impurity atoms in the interstitial position are annealed to allow them to enter the replacement position. The temperature of annealing is generally 200~800C, which is much lower than the temperature of thermal diffusion doping. Annealing principle Evaporated electrode metal annealing After evaporating the electrode metal, it needs to be annealed, so that the semiconductor surface and the metal can form an alloy for good contact (reduce contact resistance). At this time, the annealing temperature should be selected to be slightly higher than the eutectic point of the metal-semiconductor (for Si-Al alloy, it is 570 degrees). I believe that everyone has a new knowledge of the annealing principle under the introduction of Kehua Xiaobian. Xiaobian Kehua has been engaged in this industry for a period of time. If you encounter any questions that you do not understand, you can consult the editor at any time.