One-fourth of the global energy losses are spent to overcome friction, making it particularly important to reduce and minimize friction between contacting materials. Hexagonal close-packed (HCP) metals are an important class of structural materials. It has not been possible to reduce their friction, primarily because of friction-induced dislocation slip and twinning. Here, we find particularly low friction when sliding perpendicular to the -axis on the basal plane in HCP Mg single crystals. This is in contrast to the common belief that friction is small along the preferred dislocation slip direction (-axis). This macroscopic low-friction stems from twinning assisted lattice reconstruction sharing a common rotation axis, confirmed by atomistic simulations and strain energy analysis. While sliding along the -axis and other directions, 〈 + dislocation activity accounts for high frictional resistance. By unambiguously decoupling the contributions of dislocation slip and twinning, this discovery reveals potential opportunities in mitigating the energy dissipation at tribological interfaces of HCP metals, e.g. through crystallographic texture design.

中文翻译：

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通过孪晶辅助镁晶格重构实现宏观低摩擦

全球能量损失的四分之一用于克服摩擦，因此减少和最小化接触材料之间的摩擦尤为重要。六方密排（HCP）金属是一类重要的结构材料。不可能减少它们的摩擦，主要是因为摩擦引起的位错滑移和孪生。在这里，我们发现在 HCP 镁单晶的基面上垂直于 轴滑动时摩擦特别低。这与人们普遍认为沿优选位错滑移方向（轴）摩擦力很小的观点相反。这种宏观低摩擦源于共享公共旋转轴的孪生辅助晶格重建，并已通过原子模拟和应变能分析得到证实。当沿-轴和其他方向滑动时，<+位错活动导致高摩擦阻力。通过明确地解耦位错滑移和孪晶的贡献，这一发现揭示了减轻 HCP 金属摩擦界面能量耗散的潜在机会，例如通过晶体织构设计。