Industrial Application of Recrystallization Control in Aluminum Products

Abstract

Engineering properties of aluminum alloys can be optimized by a combination of thermomechanical processes. For example, a series of deformation and recrystallization processes is used to improve the deep drawing characteristics of aluminum sheet for beverage can fabrication or the forming characteristics in automotive applications. In other cases, suppression of recrystallization is desired: fracture toughness of high strength aluminum alloys is better for an unrecrystallized material than for a recrystallized material of comparable yield strength. Industrial control of recrystallization mainly focuses on control of texture for formability, control of grain size and degree of recrystallization for surface appearance and damage related properties. Such control is achieved by manipulating nucleation and growth of new grains. Nucleation density and crystallographic orientation of new grains is determined by inhomogeneities of the deformed structure. Grain boundary mobility is controlled by second phases, which at the correct size will exert a pinning force on the boundary. Additionally, solutes impose a drag on moving grain boundaries. The following will review the various applications of recrystallization in manufacturing of wrought aluminum products, summarize the current understanding of recrystallization processes in aluminum alloys, and point out needs for further understanding and necessary requirements for simulation of recrystallization processes.