发表机构
Karlsruhe Institute of Technology; ASMEC GmbH; University of Tennessee; Karlsruhe Nano Micro Facility (KNMFi)（卡尔斯鲁厄理工学院; ASMEC有限公司; 田纳西大学; 卡尔斯鲁厄纳米微设施）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究以SrTiO3为对象，探究了预制位错密度对氧化物微划痕响应的影响，发现位错可抑制弹性变形、改变裂纹形态，为位错调控近表面损伤容限提供了直接证据。
AI 中文摘要
大多数陶瓷在低载荷下有小颗粒划过表面时，会出现脆性表面损伤和开裂。微划痕试验是模拟该加载场景同时保留材料变形历史的有用技术；然而，预制位错（可显著促进塑性变形）对陶瓷的影响尚未被探究。本研究以典型钙钛矿SrTiO3为模型，探究机械预制位错对氧化物微划痕响应的影响。首先，通过室温循环布氏压头划痕引入了跨越四个数量级的各种位错密度；随后，使用标称30μm球形金刚石压头，在原始区域和位错预制区域内进行载荷递增的微划痕试验。在参考原始表面上，观察到从弹性变形到弹塑性变形的明显转变，随后在更高载荷下出现中位/径向裂纹。相比之下，预制位错伴随残余压应力，抑制了弹性变形，使中位/径向裂纹缩短，并随后转变为部分锥形裂纹。通过三维纳米CT对亚表面裂纹进行表征，利用Lawn-Evans-Marshall和Lawn-Wiederhorn-Roberts模型描述了有无位错时裂纹几何的变化。这些发现提供了位错调控近表面损伤容限的直接证据，且对其他可塑性变形的氧化物具有普遍适用性。
英文摘要
Most ceramics suffer from brittle surface damage and cracking when small particles slide across the surface under low load. Microscratching tests are a useful technique to mimic this loading scenario while retaining the material's deformation history; however, the impact of pre-seeded dislocations, which can significantly facilitate plastic deformation, has not been explored in ceramics. Here, the influence of mechanically seeded dislocations on the microscratching response of oxides is investigated using a model perovskite, SrTiO3. First, various dislocation densities over four orders of magnitude are introduced via room-temperature cyclic Brinell indenter scratching. Subsequently, load-ramped microscratching tests are performed within the pristine and dislocation-seeded regions using a nominally 30 μm spherical diamond tip. On the reference pristine surface, we observe a clear transition from elastic to elasto-plastic deformation, followed by median/radial cracking at higher loads. In contrast, pre-seeded dislocations, accompanied by residual compressive stresses, suppress elastic deformation and lead to median/radial crack shortening and subsequent transition to a partial cone crack. The subsurface cracks are characterized by 3D Nano-CT. The changes in crack geometry, with and without dislocations, were described using the Lawn-Evans-Marshall and Lawn-Wiederhorn-Roberts models. These findings provide direct evidence of dislocation-regulated near-surface damage tolerance, with general applicability to other plastically deformable oxides.
Comments23 pages, 9 figures
