Using a Berkovich pyramidal indenter and an instrumented nanoindentation platform, dual stage nanoindentation creep tests, including loading to a pre-set load and holding at the constant load then unloading, were performed on polycrystalline pure magnesium at 300 K. Indentation tests were performed at four indentation loading rates of 0.05, 0.5, 5, and 50 mN/s at constant load of 45 mN and holding time of 400 s. These were performed to assess indentation force-displacement response along with average indentation stress, indentation strain rate sensitivity and ambient temperature rate dependent plastic deformation response of the material. To this end, activation volume, a kinetic characteristic of plastic deformation, and density of mobile dislocations in plastically deforming material in the plastic zone around the indenter are discussed in detail. Uncertainties and sources of error, i.e. indentation size effect, surface roughness, and thermal drift, and pile-up/sink-in measuring creep response through nanoindentation are provided in the current paper as well. The microstructure of the material was also studied through optical and scanning electron microscopy to further investigate the microstructure/property correlations in the tested polycrystalline pure magnesium. The results show the dependency of indentation stress, strain rate sensitivity, and activation volume upon depth and loading rate. According to the creep stress exponent measurements, the dominant mechanism of rate dependent plastic deformation for polycrystalline pure Mg at ambient temperature is attributed to obstacle limited dislocation glide. Finally, the contribution of mechanical twins in the plastic zone around the indenter in the studied polycrystalline pure magnesium is briefly discussed.

使用Berkovich金字塔压头和仪器化的纳米压痕平台，在300 K的多晶纯镁上进行双阶段纳米压痕蠕变测试，包括加载至预设负载并保持恒定负载然后卸载。在45 mN的恒定载荷和400 s的保持时间下，压痕加载速率分别为0.05、0.5、5和50 mN / s。进行这些测试以评估压入力-位移响应以及材料的平均压入应力，压入应变率敏感性和与环境温度速率相关的塑性变形响应。为此，激活量是塑性变形的动力学特征，详细讨论了压头周围塑性区内塑性变形材料中的移动位错的密度和密度。本文还提供了不确定性和误差来源，即压痕尺寸效应，表面粗糙度和热漂移，以及通过纳米压痕的堆积/沉入测量蠕变响应。还通过光学和扫描电子显微镜研究了材料的微观结构，以进一步研究所测试的多晶纯镁中的微观结构/性质相关性。结果表明压痕应力，应变速率敏感性和激活体积对深度和加载速率的依赖性。根据蠕变应力指数测量，多晶纯镁在环境温度下速率依赖的塑性变形的主要机理归因于障碍物有限的位错滑移。最后，简要讨论了在所研究的多晶纯镁中压头周围塑性区中的机械孪晶的贡献。