Mg-Al based alloys are the dominant commercial magnesium alloys but suffer from inferior creep resistance at elevated temperatures, which strictly limits their application in heat-resistant components. Alloying with rare earth (RE) elements is widely recognized as a critical strategy to enhance their high-temperature performance. This paper systematically reviews the high-temperature creep behavior and strengthening mechanisms of RE-containing Mg-Al alloys. The strengthening mechanism primarily relies on the formation of heat-resistant precipitates and solute segregation. These microstructural features effectively pin dislocations and suppress grain boundary sliding, thereby significantly reducing the creep rate. Following this, current composition design methodologies are highlighted, emphasizing the application of CALPHAD, first-principles calculations, and machine learning. Subsequently, the effects of various RE and alloying elements on microstructural evolution and properties are critically analyzed. Building on the understanding of these strengthening mechanisms, an ideal microstructural architecture tailored for superior creep resistance is proposed, which is distinctly characterized by a robust, thermally stable grain boundary skeleton to suppress grain boundary sliding, coupled with high-density intragranular nano-dispersoids to effectively pin dislocation motion. Furthermore, the influence of processing technologies—casting, heat treatment and thermomechanical processing—on creep performance is summarized. Finally, future development trends are outlined, specifically focusing on innovations in multi-scale integrated computational design, microstructural regulation, and synergistic processing technologies. Such strategies are expected to accelerate the development of next-generation heat-resistant magnesium alloys, satisfying the stringent requirements of aerospace and automotive applications.

Recrystallization stands as an essential process that influences the microstructure and properties of magnesium (Mg) alloys, yet its mechanisms remain complex and multifaceted. This review explores the key factors affecting the recrystallization behavior of Mg alloys, emphasizing how their unique structural characteristics impact the driving forces and dynamics of recrystallization. Unlike conventional alloys, Mg alloys exhibit distinctive recrystallization kinetics, which is significantly affected by deformation conditions, such as strain rate, temperature, and processing methods (e.g., rolling, forging, and extrusion). The process is also influenced by material characteristics, including initial grain size, texture, dislocation density, solute clustering, and stacking fault energy. Additionally, uneven strain distribution, stress concentrations, and stored energy play crucial roles in shaping the formation of recrystallized grains, particularly near grain boundaries. Notably, recrystallization is driven by dislocation accumulation and the availability of slip systems, with new strain-free grains typically forming in regions of high dislocation density. This paper synthesizes the existing literature to provide a comprehensive understanding of the mechanisms and kinetics of recrystallization in Mg alloys, highlighting the influence of microstructural features such as second-phase particles and grain boundary characteristics. It also identifies key challenges and suggests promising directions for future research, including optimizing material compositions and the interaction between deformation conditions via machine learning.

Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium (Mg) alloys. Specifically, twins play a crucial role in initiating dynamic recrystallization (DRX), while twin regions experience rapid recrystallization during static recrystallization (SRX). The activation of twinning can lead to changes in lattice orientation, significantly impacting the final texture in Mg alloys. The active roles of twinning are influenced by various factors during the activation process, and the mobility of twin boundaries (TB) can be amplified by stress effects, dislocation interactions, and thermal effects. Conversely, annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them, restraining their motion. Events such as segregation may also alter the twinning propensity in Magnesium-rare earth (Mg-RE) alloys. While {10–11} contraction twins (CT) and {10–11}-{10–12} double twins (DT) can promote dynamic recrystallization (DRX), they also pose a risk as potential sources of voids and cracks. Additionally, understanding the nucleation and growth mechanisms of twinning is crucial, and these aspects are briefly reviewed in this article. Considering the factors mentioned above, this article summarizes the recent research progress in this field, shedding light on advancements in recent eras.

High temperature performance of magnesium alloys can be tailored by either grain size or precipitates in the grain interior. In this study, exceptional creep resistance was successfully acquired in a RE-free cast Mg-Al-Ca-Ti (AC51Ti) alloy. Microalloying of Ti (0.01 wt.%) has been found to be beneficial to the improvement of the tensile creep resistance in a RE-free cast Mg-5Al-0.35Mn-(1Ca) (AC51) alloy, showing a low state creep rate (SCR) of 2.70 × 10⁻⁹ s⁻¹ at 200 ℃/50 MPa, which is even better than that of many reported RE-containing Mg alloys. The presence of trace Ti contributes to the substantial refinement and more uniform distribution of Al₂Ca precipitates in the matrix. At the same time, the microalloying of Ti improves the solubility of Al and Ca in the matrix. It is reasonable to believe that the microalloying of Ti induced re-organization of Al₂Ca precipitates, dissolved a larger amount of Al and Ca atoms into magnesium lattice, and increased the possibility of interaction between GB/dislocations and precipitates, which strongly correlates with the high temperature properties. The creep strengthening mechanisms primarily attributed to both second phase strengthening and solid solution strengthening were separately proposed based on the experimental investigations.