fcc等原子比VCoNi中熵合金因优异的力学性能受到广泛关注，而探究其塑性变形机制对于力学性能调控至关重要。为了探究晶粒取向对位错运动过程和位错间相互作用的影响机理，本工作利用纳米压痕实验探讨了VCoNi中熵合金{101}、{111}和{001}晶粒的塑性变形行为。通过滑移台阶演变和载荷-位移曲线的分析，重点研究了晶体取向对其塑性变形行为的影响，以及位错间相互作用、载荷-位移变化行为与位错运动之间的关系。结果表明，VCoNi中熵合金中晶粒取向决定纳米压痕诱导滑移系的激活与开动顺序，以及位错反应过程，进而显著影响压痕压坑和其周边滑移台阶的形貌，以及载荷-位移变化行为。位错相互作用的分析结果表明，位错反应易在{101}晶粒中形成Lomer-Cottrell位错锁和Glissile结，在{111}晶粒中易形成Collinear结和Lomer-Cottrell位错锁，而在{001}晶粒中易形成Glissile结，这决定不同晶粒压痕载荷-位移曲线中的后续位移突变行为。

High- and medium-entropy alloys have attracted considerable attention because of their innovative design concepts. The VCoNi medium-entropy alloy with equiatomic ratio, a distinctive type of medium-entropy alloy, is characterized by a fcc structure. As it exhibits remarkable mechanical properties such as strength and plasticity across a broad temperature spectrum, it is suitable for versatile applications. Current research on VCoNi medium-entropy alloys predominantly focuses on the alloy design and the manipulation of heat treatment technologies to enhance mechanical properties with relatively less emphasis on elucidating plastic deformation mechanisms. A profound understanding of these mechanisms is imperative for controlling their properties. Although previous studies have revealed plastic deformation mechanisms mediated by dislocations in VCoNi medium-entropy alloys, the impact of grain orientation on dislocation movement and interaction mechanisms remains elusive. Nanoindentation technology has been widely used to assess plastic deformation behavior and dislocation evolution in materials. Grain orientation profoundly influences the mechanical properties and plastic deformation behavior of materials at the microscale. Therefore, investigating the influence of grain orientation on the plastic deformation mechanism in the VCoNi medium-entropy alloy is of great importance. A comprehensive understanding of plastic deformation and dislocation interactions can be achieved by analyzing slip steps generated by nanoindentation. This study delves into the plastic deformation behavior of VCoNi medium-entropy alloy in {101}, {111}, and {001} grains using nanoindentation. By analyzing the evolution of slip steps and load-displacement curves, it concentrates on the influence of crystal orientation on plastic deformation behavior and explores the intricate relationship among dislocation interactions, load-displacement behavior, and dislocation motion. The grain orientation in the VCoNi medium-entropy alloy dictates the activation and sequence of slip systems induced by nanoindentation, thereby substantially influencing the morphology of indentations, surrounding slip steps, and load-displacement behavior. The slip steps on the same slip plane in each grain preferentially appear on a positively inclined slip plane. On {101} grains, the slip steps appear on the (111) and (\mathrm{11}\overline{\mathrm{1}}) slip planes initially, and then on the (\mathrm{1}\overline{\mathrm{1}}\overline{\mathrm{1}}) and (\mathrm{1}\overline{\mathrm{1}}\mathrm{1}) slip planes. In {111} grains, the slip steps appear on the (\mathrm{11}\overline{\mathrm{1}}), (\mathrm{1}\overline{\mathrm{1}}\overline{\mathrm{1}}), and (\mathrm{1}\overline{\mathrm{1}}\mathrm{1}) slip planes. On {001} grains, the slip steps appear on the four {111} slip planes. {101}, {111}, and {001} grains exhibit butterfly-shaped, nested triangle-shaped, and cross-shaped overall indentation morphologies, respectively. Additionally, only a limited occurrence of double cross-slip is observed at the edges of the slip steps in {101} and {001} grains. The analysis of dislocation interactions revealed that on {101} grains, dislocation reactions tended to form Lomer-Cottrell locks and Glissile junctions, in {111} grains they tended to form Collinear junctions and Lomer-Cottrell locks, and in {001} grains they tended to form Glissile junctions. This determination influences the subsequent pop-in behavior in the load-displacement curves of different grains.