Abstract Elevated temperature nanoindentation measurements were performed on polycrystalline tungsten to 950 °C under high vacuum conditions with very low thermal drift. The temperature dependence of the hardness, elastic modulus, strain rate sensitivity, activation volume and the indentation size effect in hardness were studied. More significant time-dependent deformation was observed from 850 °C. Strain rate sensitivity determined by analysis of indentation creep data increased with temperature. Activation volume reached a peak of ~50 b3 at 750–800 °C. Decreasing activation volume >800 °C was a consequence of the increased strain rate sensitivity. For a bcc metal lattice resistance depends on T/Tc (where Tc, the critical temperature, at which flow stress becomes insensitive to temperature, is 527 °C for W); size effects would be expected scale with this relative temperature. Stronger indentation size effects in hardness were found at elevated temperatures. The influence of the time-dependent deformation on the unloading data was accounted for by a viscoelastic compliance correction. After correction the elastic moduli were to within ~1% of literature values at 750–800 °C and to within 6% at 950 °C. These small remaining differences are consistent with AFM measurements which show that pile-up is significant in these high temperature indentations.

中文翻译：

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从 25 到 950 °C 的多晶钨中应变率敏感性、压痕尺寸效应和堆积的温度依赖性

摘要 在高真空条件下对多晶钨进行高温纳米压痕测量至 950 °C，热漂移非常低。研究了硬度的温度依赖性、弹性模量、应变率敏感性、活化体积和硬度对压痕尺寸的影响。从 850 °C 观察到更显着的时间相关变形。通过分析随温度增加的压痕蠕变数据确定的应变率敏感性。活化体积在 750–800 °C 时达到 ~50 b3 的峰值。减少活化体积 > 800 °C 是应变率敏感性增加的结果。对于 bcc 金属晶格电阻取决于 T/Tc（其中 Tc 是临界温度，此时流动应力对温度不敏感，W 为 527 °C）；尺寸效应会随着这种相对温度而扩大。在升高的温度下发现了更强的压痕尺寸对硬度的影响。随时间变化的变形对卸载数据的影响由粘弹性柔量修正来解释。校正后，弹性模量在 750–800 °C 时在文献值的约 1% 以内，在 950 °C 时在 6% 以内。这些小的剩余差异与 AFM 测量结果一致，这表明在这些高温压痕中堆积是显着的。校正后，弹性模量在 750–800 °C 时在文献值的约 1% 以内，在 950 °C 时在 6% 以内。这些小的剩余差异与 AFM 测量结果一致，这表明在这些高温压痕中堆积是显着的。校正后，弹性模量在 750–800 °C 时在文献值的约 1% 以内，在 950 °C 时在 6% 以内。这些小的剩余差异与 AFM 测量结果一致，这表明在这些高温压痕中堆积是显着的。