Abstract We report a coupled in-situ micro-Laue diffraction and nano-indentation experiment, with spatial and time resolution, to investigate the deformation mechanisms in [001]-oriented single crystal MgO. Crystal plasticity finite element modelling was applied to aid interpretation of the experimental observations of plasticity. The Laue spots showed both rotation and streaking upon indentation that is typically indicative of both elastic lattice rotation and plastic strain gradients respectively in the material. Multiple facets of streaking of the Laue peaks suggested plastic slip occurring on almost all the {101}-type slip planes oriented 45° to the sample surface with no indication of slip on the 90° {110} planes. Crystal plasticity modelling also supported these experimental observations. Owing to asymmetric slip beneath the indenter, as predicted by modelling results and observed through Laue analysis, sub-grains were found to nucleate with distinct misorientation. With cyclic loading, the mechanical hysteresis behaviour in MgO is revealed through the changing profiles of the Laue reflections, driven by reversal of plastic strain by the stored elastic energy. Crystal plasticity simulations have also shown explicitly that in subsequent loading cycles after first, the secondary slip system unloads completely elastically while some plastic strain of the primary slip reverses. Tracking the Laue peak movement, a higher degree of lattice rotation was seen to occur in the material under the indent, which gradually decreased moving laterally away. With the progress of deformation, the full field elastic strain and rotation gradients were also constructed which showed opposite lattice rotations on either sides of the indent.

中文翻译：

---

结合原位纳米压痕和微劳厄衍射的[001]取向MgO的变形行为

摘要 我们报道了具有空间和时间分辨率的耦合原位微劳厄衍射和纳米压痕实验，以研究 [001] 取向单晶 MgO 的变形机制。晶体塑性有限元建模被用于帮助解释塑性的实验观察。劳厄点在压痕时显示旋转和条纹，这通常分别表示材料中的弹性晶格旋转和塑性应变梯度。劳厄峰条纹的多个方面表明塑性滑移发生在几乎所有与样品表面成 45° 的 {101} 型滑移平面上，而在 90° {110} 平面上没有任何滑移迹象。晶体塑性模型也支持这些实验观察。由于压头下方的不对称滑动，正如建模结果所预测并通过劳厄分析观察到的那样，发现亚晶粒以明显的错误取向成核。在循环加载的情况下，MgO 中的机械滞后行为通过劳厄反射的变化曲线来揭示，这是由储存的弹性能的塑性应变反转驱动的。晶体塑性模拟还明确表明，在第一次之后的后续加载循环中，次滑移系统完全弹性卸载，而主滑移的一些塑性应变反转。跟踪劳厄峰运动，在凹痕下的材料中看到更高程度的晶格旋转，并逐渐减少横向移开。随着变形的进行，