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 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.