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.

Although mechanically fastened joints are generally considered a mature technology, significant problems still exist with their use, among which the preload loss in pretensioned bolts is a major one. This paper has investigated two key issues in structural durability design for mechanically fastened composite joints, i.e. temperature–time-dependent behavior for viscoelastic preload relaxation and prediction method for its long-term performance. Towards this purpose, a two-phase experimental program was conducted consisting of short- and long-term joint relaxation tests. Phase I monitored the short-term fastener preload relaxation (up to 36 h), with a special self-made bolt strain sensor. Phase II utilized the time–temperature superposition principle to establish a method of using short-term relaxation curves to construct the long-term master curve (accelerated test). It was found that there was a significant loss of bolt preload when temperature and initial preload increased, and the relaxation rate of composited joint was much larger than that of the metallic joint. Based on the strong temperature dependence of bolt relaxation, accelerated characterization was conducted for long-term behavior. Furthermore, to quantitatively relate the relaxation data to a model equation, a new preload prediction model was developed based on the creep total-strain theory. Comparisons of the prediction model and accelerated test results indicated that the improved model provided better accuracy than existing models such as Shivakumar–Crews’s and Hook-Norton’s models for describing the long-term preload behavior.