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Temperature-dependent size effects on the strength of Ta and W micropillars

  • The strength of metals increases with decreasing sample size, a trend known as the size effect. In particular, focused ion beam-milled body-centered cubic (BCC) micropillars exhibit a size effect known to scale with the ratio of the test temperature to the critical temperature (Tc) of the BCC metal, a measure of how much the yield stress is governed by the lattice resistance. In this paper, this effect is systematically studied by performing high-temperature compression tests on focused ion beam-manufactured Ta and W single crystal pillars ranging in diameter from 500 nm to 5 μm at temperatures up to 400 °C, and discussed in the context of bulk strength and size dependent stresses. Both metals show larger size effects at higher temperatures, reaching values that are in the range of FCC metals at temperatures near Tc. However, it is demonstrated that size effects can be considerably affected by material parameters such as dislocation density and lattice friction, as well as by the yield criterion used. Furthermore, for W, a change from uniform wavy deformation to localized deformation is observed with increasing temperature and pillar size, further indicating that the temperature ratio strongly influences the relative motion of screw and edge dislocations.

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Document Type:Article
Author:Oscar Torrents AbadORCiD, Jeffrey M. WheelerORCiD, Johann MichlerORCiD, Andreas S. Schneider, Eduard ArztORCiD
Parent Title (English):Acta Materialia
First Page:483
Last Page:494
Year of first Publication:2016
Release Date:2022/11/18
Tag:compression test; crystal plasticity; micropillar; size effect
Impact:05.301 (2016)
Funding Information:European Union's Seventh Framework Program (FP/2007-2013)/ERC Advanced Grant Agreement No. 340929.
Scientific Units:Functional Microstructures
Open Access:Open Access
Signature:INM 2016/003
Licence (German):License LogoCreative Commons - CC BY-NC-ND - Namensnennung - Nicht kommerziell - Keine Bearbeitungen 4.0 International