Strength statistics of single crystals and metallic glasses under small stressed volumes

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• 作者：Yanfei Gao^a ; ^b ; ^{ygao7@utk.edu" class="auth_mail" title="E-mail the corresponding author} ; ^{gaoy@ornl.gov" class="auth_mail" title="E-mail the corresponding author} ; Hongbin Bei^a ; ^{beih@ornl.gov" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Strength statistics ; Intrinsic thermal-activation mechanism ; Extrinsic stochastic mechanism ; Universal relationship between strength and sample size
• 刊名：Progress in Materials Science
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：82
• 期：Complete
• 页码：118-150
• 全文大小：5976 K

文摘

It has been well documented that plastic deformation of crystalline and amorphous metals/alloys shows a general trend of “smaller is stronger”. The majority of the experimental and modeling studies along this line have been focused on finding and reasoning the scaling slope or exponent in the logarithmic plot of strength versus size. In contrast to this view, here we show that the universal picture should be the thermally activated nucleation mechanisms in small stressed volume, the stochastic behavior as to find the weakest links in intermediate sizes of the stressed volume, and the convolution of these two mechanisms with respect to variables such as indenter radius in nanoindentation pop-in, crystallographic orientation, pre-strain level, sample length as in uniaxial tests, and others. Experiments that cover the entire spectrum of length scales and a unified model that treats both thermal activation and spatial stochasticity have discovered new perspectives in understanding and correlating the strength statistics in a vast of observations in nanoindentation, micro-pillar compression, and fiber/whisker tension tests of single crystals and metallic glasses.