reanneals

Reannealing is a thermal treatment process in which a material that has undergone prior processing or stress is heated again to a chosen temperature, held for a period, and then cooled in a controlled manner. The purpose is to relieve residual stresses, restore ductility, and/or adjust the microstructure after previous work such as cold deformation, welding, or previous annealing. Reannealing can be used to reverse work hardening and to re-establish desirable mechanical properties.

In metals and alloys, reannealing typically follows cold work or welding. The material is heated to a temperature sufficient to enable recovery and/or recrystallization, depending on the alloy and desired outcome, and then cooled slowly or at a controlled rate. The process can reduce hardness, lower yield strength, and increase ductility, while potentially causing some grain growth or oxidation if performed in air. The specific temperature and time depend on the metal system and the starting condition.

In glass and ceramics, reannealing serves to relieve thermal stresses introduced during forming or shaping. The glass is heated to a temperature below the softening point, held, and cooled slowly to reduce birefringence and the risk of cracking. Reannealing is distinct from primary glazing or annealing in that it targets stresses accumulated after previous shaping processes.

Considerations for reannealing include the material’s composition, prior history, desired properties, potential for grain growth or oxidation, and the choice of atmosphere. It is not universally required and may be avoided if it adversely affects strength or other critical properties.