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arXiv 2108.09050cond-mat.mtrl-sci
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电子背散射衍射揭示的摩擦诱导晶体转动运动学

Tribologically induced crystal rotation kinematics revealed by electron backscatter diffraction

Christian Haug, Dmitri Molodov, Peter Gumbsch, Christian Greiner

摘要:

金属的摩擦学载荷通过位错介导的塑性形变引起微观结构变化。在连续滑动过程中,剪切和晶格旋转的组合导致形成影响滑动界面处的摩擦和磨损的晶体织构。为了阐明在这个过程中所涉及的基本晶格旋转运动学在早期阶段的滑动,我们进行了无润滑,线性单程滑动实验上的铜双晶体蓝宝石球。直接在晶界附近磨损痕迹的本体表面上进行的电子背散射衍射(EBSD)显示晶格旋转约高达35°。主要是,摩擦引起的晶体旋转似乎是运动学约束的横向(TD)周围的旋转,并发生在两个晶粒,无论负载(2至8 N)。我们证明,反转滑动方向(SD)反转晶体旋转的意义,但不改变大多数索引EBSD数据的旋转的主要性质。较低比例的晶格围绕TD旋转得更远(大约高达90°),伴随着围绕+/-SD的叠加晶体旋转。分析表明,滑动方向和晶粒取向发挥了系统的影响,如何晶体旋转被容纳。这是合理的几何形状,各向异性磨损轨迹轮廓和滑动痕迹。在特定的条件下,观察到晶体旋转和孪生的组合。这些详细的洞察摩擦诱导晶格旋转运动学的基本性质提供了重要的指导应用研究目标材料具有优异的摩擦性能。

英文摘要:

Tribological loading of metals induces microstructural changes by dislocation-mediated plastic deformation. During continued sliding, combined shear and lattice rotation result in the formation of crystallographic textures which influence friction and wear at the sliding interface. In order to elucidate the fundamental lattice rotation kinematics involved in this process during the early stages of sliding, we conducted unlubricated, linear single pass sliding experiments on a copper bicrystal using sapphire spheres. Electron backscatter diffraction (EBSD) performed directly on the bulk surface of the wear tracks in the vicinity of the grain boundary reveals crystal lattice rotations by approximately up to 35°. Predominantly, the tribologically induced crystal rotations appear to be kinematically constrained to rotations around the transverse direction (TD) and occur in both grains, irrespective of load (2 to 8 N). We demonstrate that inverting the sliding direction (SD) inverts the sense of crystal rotation, but does not change the principal nature of rotation for the majority of indexed EBSD data. A lower proportion of the crystal lattice rotates much farther around TD (roughly up to 90°), accompanied by a superimposed crystal rotation around +/-SD. Analysis reveals that sliding direction and grain orientation exert a systematic influence of how crystal rotations are accommodated. This is rationalized in terms of geometry, anisotropic wear track profiles and slip traces. Under specific conditions, combined crystal rotation and twinning are observed. These detailed insights into the fundamental nature of tribologically induced lattice rotation kinematics provide important guidance for applied research targeting materials with superior tribological properties.

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