Abstract This study investigates the effects of the initial grain size and temperature (ranging from room temperature to 1100 °C) on the mechanical properties and microstructure evolution of Ti2AlC MAX phase. A Hall-Petch like relationship is observed between compressive strength and the grain size below brittle-to-plastic transition temperature (BPTT). However, the compressive strength of fine-grained MAX phase decreases more rapidly with increasing temperature resulting in inverse Hall-Petch effect above BPTT. Results from postmortem EBSD analysis reveal complex microstructural evolution in both fine- and coarse-grained microstructures during loading at different temperatures. The pronounced drop in compressive strength for fine-grained microstructures at temperatures close to BPTT is attributed to creep induced grain boundary sliding resulting in texture development with more grains oriented for easy slip. In coarse-grained microstructures, no significant texture development is observed even though grain refinement occurs at all temperatures. A mathematical model has also been formulated to predict the experimentally observed grain size and temperature dependent variation in the compressive strength of Ti2AlC over a wide range of grain sizes and test temperatures. The mathematical model accounts for the competing effects of Hall-Petch strengthening and high temperature creep induced softening mechanisms.

中文翻译：

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Ti2AlC 在 25-1100°C 温度范围内压缩时的力学性能和显微组织演变

摘要 本研究研究了初始晶粒尺寸和温度（从室温到 1100 °C）对 Ti2AlC MAX 相力学性能和微观结构演变的影响。在抗压强度和低于脆塑性转变温度 (BPTT) 的晶粒尺寸之间观察到类似 Hall-Petch 的关系。然而，细晶 MAX 相的抗压强度随着温度的升高而下降得更快，导致 BPTT 以上的逆霍尔-佩奇效应。来自尸检 EBSD 分析的结果揭示了在不同温度下加载期间细晶粒和粗晶粒微观结构的复杂微观结构演变。在接近 BPTT 的温度下，细晶粒显微组织的抗压强度显着下降，这归因于蠕变引起的晶界滑动，导致织构发展，更多晶粒取向易于滑动。在粗晶粒显微组织中，即使在所有温度下都发生晶粒细化，也没有观察到显着的织构发展。还制定了一个数学模型来预测实验观察到的晶粒尺寸和温度相关的 Ti2AlC 抗压强度在很宽的晶粒尺寸和测试温度范围内的变化。数学模型解释了霍尔-佩奇强化和高温蠕变诱导软化机制的竞争效应。即使在所有温度下都发生晶粒细化，也没有观察到显着的织构发展。还制定了一个数学模型来预测实验观察到的晶粒尺寸和温度相关的 Ti2AlC 抗压强度在很宽的晶粒尺寸和测试温度范围内的变化。数学模型解释了霍尔-佩奇强化和高温蠕变诱导软化机制的竞争效应。即使在所有温度下都发生晶粒细化，也没有观察到明显的织构发展。还制定了一个数学模型来预测实验观察到的晶粒尺寸和温度相关的 Ti2AlC 抗压强度在很宽的晶粒尺寸和测试温度范围内的变化。数学模型解释了霍尔-佩奇强化和高温蠕变诱导软化机制的竞争效应。