A new regime for mechanical annealing and strong sample-size strengthening in body centred cubic molybdenum

A new regime for mechanical annealing and strong sample-size strengthening in body centred cubic molybdenum

Because of crystal symmetry, body centred cubic (BCC) metals have large differences in lattice friction between screw and edge dislocations, and manifest generally different mechanical behaviours from face centred cubic (FCC) metals. Although mechanical annealing (significant drop in stored dislocat...

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Bibliographic Details
Main Authors: Huang, Ling (Author), Li, Qing-Jie (Author), Shan, Zhi-Wei (Author), Li, Ju (Contributor), Sun, Jun (Author), Ma, Evan (Author)
Other Authors: Massachusetts Institute of Technology. Department of Materials Science and Engineering (Contributor), Massachusetts Institute of Technology. Department of Nuclear Science and Engineering (Contributor)
Format: Article
Language:English
Published: Nature Publishing Group, 2015-04-30T14:29:24Z.
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Summary:Because of crystal symmetry, body centred cubic (BCC) metals have large differences in lattice friction between screw and edge dislocations, and manifest generally different mechanical behaviours from face centred cubic (FCC) metals. Although mechanical annealing (significant drop in stored dislocation density in response to applied stress) has been observed in FCC metals, it has not been observed in BCC metals so far. Here we show that significant mechanical annealing does occur in BCC Mo pillars, when their diameters decrease to hundreds of nanometers. In addition, there exists a critical diameter for focused ion beam milled pillars, below which the strengthening exponent increases dramatically, from ~0.3 to ~1. Thus, a new regime of size effects in BCC metals is discovered that converges to that of FCC metals, revealing deep connection in the dislocation dynamics of the two systems.
National Natural Science Foundation (China) (Grant 50925104)
National Natural Science Foundation (China) (Grant 50720145101)
National Natural Science Foundation (China) (Grant 50831004)
National Basic Research Program of China (973 Program) (Grant 2010CB631003)
National Basic Research Program of China (973 Program) (Grant 2012CB619402)
National Science Foundation (U.S.) (CMMI-0728069)
National Science Foundation (U.S.) (DMR-1008104)
National Science Foundation (U.S.) (DMR-1120901)
United States. Air Force Office of Scientific Research (FA9550-08-1-0325)

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