A Review of Microstructural Evolution and Modelling of Aluminium Alloys under Hot Forming Conditions

Abstract

Microstructural evolution during hot forming of aluminium alloys plays a critical role in both the material flow behaviour during the deformation and the post-form mechanical properties in service. This paper presents a comprehensive review on the recrystallisation mechanisms, the interrelations between microstructures and macroscopic responses, and the associated modelling methods for aluminium alloys under hot forming conditions. Particular attention is focused on dynamic recrystallisation (DRX), which occurs during hot forming. The mechanisms, key features, and conditions of occurrence (forming temperature, strain rates, etc.) during hot forming for each type of DRX type are classified. The relationships between microstructures and macroscopic responses, including the flow behaviour, the post-form strength and ductility, are summarised based on existing experimental results. Most importantly, the associated modelling work, describing the recrystallisation and the viscoplastic behaviour under hot forming conditions, is grouped into four types, to enable a clear and concise understanding of the existing quantitative micro–macro interactions, which are particularly valuable for the future development of advanced physically based multi-scale modelling work for hot-forming processes in aluminium alloys.

Influence of Hot Deformation on the Precipitation Hardening of High-Strength Aluminum AA7075 during Thermo-Mechanical Processing

“…At low forming temperatures, when no recrystallization occurs, plastic deformation can lead to a dramatic increase in dislocation density [50]. At higher temperatures, in contrast, plastic deformation promotes the activation of softening mechanisms, such as dynamic recrystallization, which ultimately reduce the dislocation density by consuming dislocations, and grain boundary migration by the coarsening of subgrains [51][52][53]. Therefore, a lower dislocation density than expected was obtained at 420 • C for the 10%-formed material, which did not promote the nucleation of precipitates or accelerate the precipitation kinetics.…”

Microhardness and tensile strength of electrochemically synthesized nickel-cobalt binary alloy sheets exfoliated from a dumbbell-shaped titanium cathode

“…The strength of the material increased because the formation of stable grain boundaries suppressed the dislocation release. In contrast, ductility significantly decreases when the grain size decreases to 1 μm or less [52,53]. In addition, no dislocations form inside the crystal grains when the grain size is less than 20 nm [54].…”

Hot Sheet Metal Forming Strategies for High‐Strength Aluminum Alloys: A Review—Fundamentals and Applications

“…At higher forming temperatures ranging from 450 to 520 °C, different types of dynamic recrystallization phenomena, including continuous, discontinuous, and geometrical dynamic recrystallization, [127,128] are believed to occur in the precipitationhardenable aluminum alloy AA7075. [129] However, continuous dynamic recrystallization is reported to be the main softening mechanism, while the occurrence of geometrical dynamic recrystallization is reported only at deformation temperatures below 520 °C.…”