Magnesium alloys are prone to hot tearing during solidification, which severely limits their widespread application. Current research on hot tearing tends to establish direct correlations between apparent factors (such as alloy composition and process conditions) and hot tearing susceptibility, which easily falls into the cognitive misunderstanding of monotonous change. In fact, alloy compositions and process conditions mainly affect the nucleation-propagation-feeding of hot tearing by regulating thermophysical parameters and microstructure, thereby improving the hot tearing resistance. Therefore, with a focus on nucleation-propagation-feeding, this paper summarizes the hot tearing theories, criteria, simulation technologies, research methods and influencing factors. It systematically reveals the direct influence mechanisms of key factors (such as thermophysical parameters and microstructure) on the nucleation-propagation-feeding of hot tearing, providing theoretical support for optimizing apparent factors like alloy composition and process conditions to precisely control the hot tearing behavior of magnesium alloys.

Magnesium (Mg) alloys have attracted considerable attention in the automotive and aerospace industries due to their exceptional lightness, high specific strength, and excellent castability. However, their susceptibility to fatigue failure poses significant challenges for the long-term service under cyclic loading. This review systematically explores the precipitation behavior in the representative rare-earth containing magnesium (Mg-RE) alloys and examines the critical role of precipitates in influencing fatigue behavior. The alloying elements and heat treatment play a pivotal role in affecting the precipitation behavior of the Mg-RE alloys. Notably, the β′, β″, and 14H long-period stacking ordered (LPSO) phases serve as primary strengthening precipitates in the Mg-Gd (Y), Mg-Nd, and Mg-RE-Zn based alloys, respectively. The size, quantity, and distribution of these precipitates can be finely controlled through the optimization of aging treatment parameters. Based on the fundamental principles for enhancing fatigue resistance, this review offers a detailed analysis of the effects of precipitates on fatigue behavior, addressing key aspects such as crack initiation, propagation, and fatigue failure under high-cycle fatigue (HCF) conditions. Besides, the effects of precipitates on the cyclic stress response, cyclic deformation characteristics, and fatigue life under low-cycle fatigue (LCF) conditions are systematically summarized. The influence of precipitates on fatigue behavior of Mg-RE alloys is primarily attributed to the mechanisms such as dislocation pinning, crack path deflection, precipitation strengthening, and the suppression of twinning. This review highlights the significance of precipitation behavior in optimizing fatigue resistance and provides valuable insights into future research directions for advancing Mg-RE alloys in the fatigue-critical structural applications.

Magnesium and its alloys offer lightweight advantage and have extensive development prospects, particularly in aerospace. However, their flammability poses a significant barrier on the development of Mg alloys. The ignition resistance of these alloys often depends on the protectiveness of the oxide film formed on the surface. This paper elucidates the formation mechanism of oxide film from thermodynamics and kinetics, classifying oxide films based on their layered structure to assess their protective properties. Furthermore, it comprehensively reviews the impact of characteristics on the protective effectiveness such as compactness, continuity, thickness, and mechanical properties. The paper also introduces various characterization methods for the microstructure and properties of oxide film. The primary objective of this paper is to enhance the comprehension of oxide film concerning the ignition resistance of Mg alloys and to furnish references for future advancements and research in Mg alloys with heightened ignition resistance.

In our previous work, die cast LA42 (Mg–4La–2.5Al–0.3Mn, wt.%) alloy with an excellent combination of thermal-conducting performance and mechanical properties was developed. This study, taking commercial die cast AZ91 (Mg-9Al-1 Zn, wt.%) alloy as a comparison, investigates the microstructure and corrosion behavior of the LA42 alloy in chloride-containing environment. The findings revealed that the microstructure of die cast LA42 alloy displays an Al-depleted α-Mg dendrite and a network shape eutectic phase comprising of eutectic α-Mg and lamellar Al₁₁La₃. The LA42 alloy exhibited slightly inferior corrosion resistance and deeper corrosion pits than the AZ91 alloy, which were related to the interphase attack and the presence of a layer of corrosion products containing more magnesium hydroxide of the LA42 alloy. The corrosion behavior of the LA42 alloy was characterized by an interphase attack on the periphery of Al-depleted α-Mg dendrite adjacent to Al₁₁La₃, which primarily ascribed to the relatively lower potential of the Al-depleted α-Mg phase and the interfacial reactivity between it and the adjacent Al₁₁La₃, whereas the AZ91 alloy showed a trait of preferential corrosion of the interior of α-Mg dendrite for its lowest potential among different phases. This comprehensive research can provide a guidance for future alloy design of Mg-Al-La alloys and their industrial applications.

The effect of Ce content (0–1.6 wt.%) on the modification of Mg₂Si phase in the as-cast Mg-5Al-2Si alloy was investigated. The original Chinese script type Mg₂Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element. The length of Chinese script type Mg₂Si phase was reduced from 110 to 50 µm with increasing Ce content to 1.6 wt.%. The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi₂ phase, which could serve as the heterogeneous nucleation of Mg₂Si phase due to the small lattice mismatch of 7.97%. The modification of Mg₂Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg₂Si phase and CeSi₂ promoted the nucleation of Mg₂Si phase. With increasing Ce content from 0 wt.% to 1.6 wt.%, the YS, UTS and EL at 150 ℃ were improved from 67.7 MPa, 91.2 MPa and 1.6% to 84.2 MPa, 128 MPa and 7.5%, respectively.