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论文题目： Experimental study and crystal plasticity finite element simulations of nano-indentation-induced lattice rotation and the underlying mechanism in TC6 single α-grain

发表时间：Available online 13 December 2019

刊源：Materials and Design 188 (2020) 108423 [ 点击下载PDF ]

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Atomic Force Microscopy (AFM) three-dimensional topography of the sample and the simulated height cloud image, it can be seen that the pile-up in the middle of the indentation boundaries is more significant than in the other regions. Extract the surface height of the sample along the axis of the indentation from the simulation result and compare it with the measurement result of the corresponding position of the AFM. As the figure shows, the final indentation depth is 368.3 nm, which is smaller than the previously measured maximum depth of 513 nm. This indicates that after elastic-plastic deformation during the loading process, a 149.7 nm elastic rebound occurs in the subsequent unloading process.

Fig.6. Comparison of: (a) experimental and simulated morphologies of the indentation (b) height along the white arrows across the indentation.

The mapping relationship between the lattice orientations and the IPF colors can be obtained from the IPF map, where the dictionary of Euler angles with the corresponding RGB values is established. A virtual IPF map can then be obtained based on the simulated orientation information and, the lattice orientation is illustrated. A high-resolution lattice orientation map was successfully obtained through PED in the slice beneath the indentation despite the large residual stress caused by severe plastic deformation of the sample, and the experimentally determined IPF map and simulated IPF map are compared in Fig.7.

Fig.7. Microstructure inside the ASB of TI20C: (a) TEM image and diffraction pattern; (b) grain orientation distribution captured by means of PED.

Fig. 11 shows a diagram where the surface orientation is rendered with the virtual 3D IPF map, misorientation angle, and elements (extracted fromthe FEMmodels) with misorientation angles N10°. Elements at indentation depths of 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm are considered.With continuous loading and increase in the contact surface between the indenter and the sample, the area of lattice rotation expands gradually in the sample surface. Correspondingly, the rotating area is sub-divided into three parts (with quite different rotation directions) by the three inner-edges of the indenter. The lattice rotation increases with continued loading, and regions with large rotation are mainly distributed along the inner-edges. In addition, a maximum misorientation angle of ~40° occurs at an indentation depth of 500 nm, whereas the lattice rotation beneath the facet and tip of the indenter is relatively small.

Fig. 11. Through-thickness distribution of the lattice orientation and elements with misorientation angles N10°.