目的 提升TC11钛合金关键服役部件的低周疲劳性能,并突破传统表面强化技术在作用深度与机制方面的局限,探索一种基于界面调控的新型强化路径。方法 利用光学显微镜（OM）、扫描电子显微镜（SEM）、EBSD及TEM对材料显微组织进行表征,并结合Lammps分子动力学模拟分析电磁冲击过程中合金晶界演化行为。结果 经过电磁冲击处理（EST）后,EST-4试样的低周疲劳循环次数达到31 705次,相比未处理试样提升约26.7%。显微组织分析表明,与ORI试样相比,EST-4试样平均晶粒尺寸由5.4 μm增至6.8 μm,相分布基本保持不变,但α/α晶界宽度明显增加,并形成条纹状界面结构。分子动力学模拟结果表明,在特定温度与循环位移条件下,界面能显著降低,界面稳定性得到提升。创新性地提出,低能电磁冲击可诱导界面发生局部预熔并形成界面桥接结构,从而增强晶界连通性,并抑制裂纹萌生与扩展。结论 揭示了电磁强化的界面调控机制,即电磁冲击处理通过诱发界面微结构演化,进而促进界面桥接,实现界面能降低与结构稳定性提升,从而明显提高TC11钛合金的低周疲劳性能。该研究为钛合金疲劳性能提升提供了新的理论依据和技术路径。
Abstract
This study focuses on TC11 titanium alloy, a widely used material for aero-engine blades, and systematically investigates the effects of Low-Energy Electromagnetic Shock Treatment (EST) on its microstructural evolution and low-cycle fatigue (LCF) behavior. As a non-thermal surface strengthening technique, EST has demonstrated considerable potential for extending the service life of metallic materials; however, its atomistic-scale mechanisms in complex titanium alloy systems remain insufficiently understood. In the experimental stage, the TC11 alloy is machined into standard LCF specimens and subjected to electromagnetic shock loading using a high-intensity, short-pulse generator. By precisely controlling the pulse energy, an optimized EST parameter set (denoted as EST-4) is established to promote beneficial microstructural modifications while strictly avoiding macroscopic thermal damage or overheating-induced deformation. Subsequent cyclic loading tests are performed to quantitatively evaluate the fatigue life. The experimental results demonstrate that EST significantly enhances the fatigue resistance of TC11 alloy. Quantitative LCF testing indicates that the average fatigue life of the as-received (ORI) specimens is 25 032 cycles, whereas the optimized EST-4 treatment increases the fatigue life to 31 705 cycles, corresponding to a substantial improvement of 26.7%. To elucidate the underlying strengthening mechanism, a comprehensive multi-scale characterization is conducted using OM, SEM, EBSD, and TEM. The results confirm that the observed performance enhancement does not originate from conventional phase-transformation strengthening, as the volume fractions of the α and β phases remain essentially unchanged before and after treatment. However, EBSD analysis reveals a slight increase in the average grain size from 5.4 μm to 6.8 μm, accompanied by a critical evolution of grain boundary morphology. High-resolution TEM observations reveal a pronounced widening of α/α interfaces, characterized by the formation of distinctive striation-like grain boundary structures. These widened interfacial regions act as effective buffers for dislocation motion, enabling more efficient dissipation of plastic strain under cyclic loading compared with the sharp, high-energy grain boundaries present in the untreated state, thereby suppressing strain localization. Furthermore, a novel electromagnetic strengthening mechanism based on interfacial engineering is proposed. It is suggested that low-energy EST induces localized pre-melting at alloy interfaces, generating a transient high-energy state that facilitates atomic rearrangement at grain boundaries. This process leads to interface bridging, enhancing atomic continuity across grain boundaries and effectively healing micro-scale discontinuities without relying on bulk recrystallization. To verify this hypothesis at the atomistic scale, molecular dynamics (MD) simulations are performed using the LAMMPS platform. An embedded-atom method (EAM) potential is employed to simulate the grain boundary energy response under electromagnetic thermal-mechanical coupling conditions. The simulation results reveal that, within a specific transient energy window, the interfacial energy of the system decreases markedly. This reduction in interfacial energy indicates a transition toward a more thermodynamically stable boundary state, thereby directly reducing the driving force for crack nucleation at grain boundaries. In summary, the synergistic effect of EST-induced interface bridging (physical connectivity enhancement) and interfacial stabilization (energy minimization) establishes a new pathway for improving the high-cycle reliability of TC11 titanium alloy. This work not only provides experimental evidences for surface modification of high-strength titanium alloy but also offers theoretical insight into the interaction between electromagnetic fields and solid-state metal interfaces.
关键词
TC11钛合金 /
低周疲劳 /
微观组织 /
界面桥接 /
电磁冲击处理
Key words
TC11 titanium alloy /
low-cycle fatigue /
microstructure /
interface bridging /
electromagnetic shocking treatment
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基金
国家自然科学基金资助计划（52273319）
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