Abstract The damage mechanisms during high-cycle fatigue (HCF) process were systematically investigated in the in-situ TiB 2 /2024 Al-composite. It is found the HCF endurance limit of in-situ TiB 2 /2024 Al-composite is ~ 360 MPa, which is much higher than the reported ex-situ particle-reinforced composites (~ 180–300 MPa). A microstructural-based multistage damage in HCF is identified from fracture surface: Stage I (crack initiation), Stage II (stable crack propagation), and Stage III (ultimate fracture). In Stage I, the (S/θ + TiB 2 ) particles generally act as initiation sites in most cases. The nano or sub-micron TiB 2 particles can homogenize stress and reduce dislocations piling-up at grain boundaries (GBs), impeding the crack nucleation from GBs. In Stage II, the GBs, grain orientations and TiB 2 particles are the major factors for the damage behaviors. The GB effects depend on their misorientations, geometries and nearby particles. The crack propagation shows crystallographic characteristics of {100}〈001〉, {111}〈110〉 and {111}〈112〉, which have different propagation rates. For TiB 2 particles, the complex effects on the HCF damage behavior depend on their size and distribution. Considering the microstructural factors, the HCF damage mechanisms was discussed in detail and an energy model of dislocation slipping for nano or sub-micron particle-reinforced metal composites was proposed.

中文翻译：

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高周疲劳原位 TiB 2 /Al-Cu-Mg 复合材料的微观结构相关损伤机制

摘要 系统研究了原位TiB 2 /2024 Al复合材料的高周疲劳（HCF）过程中的损伤机制。发现原位 TiB 2 /2024 铝复合材料的 HCF 耐久性极限为~360 MPa，远高于报道的非原位颗粒增强复合材料（~ 180-300 MPa）。从断裂表面识别出 HCF 中基于微观结构的多阶段损伤：阶段 I（裂纹萌生）、阶段 II（稳定裂纹扩展）和阶段 III（最终断裂）。在阶段 I 中，(S/θ + TiB 2 ) 粒子在大多数情况下通常充当起始点。纳米或亚微米 TiB 2 颗粒可以使应力均匀并减少位错堆积在晶界 (GBs)，从而阻止 GBs 的裂纹形核。在第二阶段，GBs，晶粒取向和TiB 2 颗粒是损伤行为的主要因素。GB 效应取决于它们的错误方向、几何形状和附近的粒子。裂纹扩展显示出{100}〈001〉、{111}〈110〉和{111}〈112〉的晶体学特征，它们具有不同的扩展速率。对于 TiB 2 颗粒，对 HCF 损伤行为的复杂影响取决于它们的大小和分布。考虑微观结构因素，详细讨论了HCF损伤机制，提出了纳米或亚微米颗粒增强金属复合材料的位错滑移能量模型。它们具有不同的传播速率。对于 TiB 2 颗粒，对 HCF 损伤行为的复杂影响取决于它们的大小和分布。考虑微观结构因素，详细讨论了HCF损伤机制，提出了纳米或亚微米颗粒增强金属复合材料的位错滑移能量模型。它们具有不同的传播速率。对于 TiB 2 颗粒，对 HCF 损伤行为的复杂影响取决于它们的大小和分布。考虑微观结构因素，详细讨论了HCF损伤机制，提出了纳米或亚微米颗粒增强金属复合材料的位错滑移能量模型。