Fatigue failure is a significant concern for magnesium (Mg) alloy components. However, fatigue damage mechanisms of Mg alloys, particularly in the case of ratchetting–fatigue interaction at elevated temperatures, are still not well understood. In this paper, we combine experiments and theoretical analysis to investigate the high-temperature damage mechanisms of the extruded AZ31 Mg alloy, specifically focusing on the effects of ratchetting–fatigue interaction. We reveal a distinct demonstration of damage, namely the formation of microvoids in the alloy due to significant ratchetting deformation, defined as ratchetting damage. Notably, this ratchetting damage is more prevalent at higher temperatures. Considering the mesomechanics-based energy mechanisms associated with grain boundaries (or twin boundaries), a mesomechanical damage model is established to capture the ratchetting damage under elevated temperatures and large ratchetting deformations. This model can reasonably simulate the intricate process of damage evolution and predict the critical condition of microvoid or microcrack formation. This work has the potential to serve as a theoretical tool for the safety design of structures made from Mg alloys under complex mechanical and thermal conditions.

中文翻译：

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具有棘轮-疲劳相互作用效应的镁合金温度相关损伤：实验和细观力学理论

疲劳失效是镁 (Mg) 合金部件的一个重要问题。然而，镁合金的疲劳损伤机制，特别是在高温下棘轮-疲劳相互作用的情况下，仍不清楚。在本文中，我们结合实验和理论分析来研究挤压AZ31镁合金的高温损伤机制，特别关注棘轮-疲劳相互作用的影响。我们揭示了一种明显的损坏现象，即由于显着的棘轮变形而在合金中形成微孔，定义为棘轮损坏。值得注意的是，这种棘轮损坏在较高温度下更为普遍。考虑到与晶界（或孪晶界）相关的基于细观力学的能量机制，建立了细观力学损伤模型来捕获高温和大棘轮变形下的棘轮损伤。该模型可以合理模拟损伤演化的复杂过程，预测微孔或微裂纹形成的临界条件。这项工作有潜力成为复杂机械和热条件下镁合金结构安全设计的理论工具。