Critical examination of strain-rate sensitivity measurement by nanoindentation methods:: Application to severely deformed niobium
Critical examination of strain-rate sensitivity measurement by nanoindentation methods:: Application to severely deformed niobium
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DOI：
10.1016/j.actamat.2007.10.039
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发表时间：
2008-02-01
期刊：
影响因子：
9.4
通讯作者：
Sevillano, Javier Gil
中科院分区：
文献类型：
--
作者：
Alkorta, Jon;Martinez-Esnaola, Jose Manuel;Sevillano, Javier Gil
分析了两种测量等效流变应力和等效塑性应变率幂律关系的应变率敏感性指数的方法，特别注意了由热漂移率和压痕尺寸效应引起的误差。结果表明，压痕蠕变试验的分辨率和精度受这些因素的影响。另一种测定方法，即速率跃变试验，避免了热漂移和压痕尺寸效应的影响。这两种方法都适用于SRS测定纯铌样品与不同的塑性应变水平赋予等通道角挤压。结果显示了率跳试验的优越性。观察到的强烈的依赖性的室温SRS铌的位错密度和应变速率上的Peierls应力和位错密度硬化的相对贡献的流动应力的样品满意地解释。(C)2007 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Two different techniques for measuring the strain-rate sensitivity (SRS) exponent, in, of the power law relating the equivalent flow stress and the equivalent plastic strain rate are analyzed, paying special attention to the errors induced by the thermal drift rate and by the indentation-size effect. It is shown that the resolution and accuracy of indentation-creep tests are affected by these factors. An alternative method of in determination, the rate-jump test, avoids the influence of both the thermal drift and the indentation-size effect. Both methods are applied to the SRS determination of pure niobium samples with different plastic strain levels imparted by equal channel angular pressing. The results show the advantages of the rate-jump test. The observed strong dependence of the room temperature SRS of niobium on its dislocation density and on the strain rate are satisfactorily explained by the relative contributions of the Peierls stress and the dislocation density hardening to the flow stress of the samples. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.