title: A new regime for mechanical annealing and strong sample-size strengthening in body             centred cubic molybdenum.
abstract: 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.
authors: Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
authors: Ling
authors: L
authors: Huang
authors: Qing-Jie
authors: QJ
authors: Li
authors: Zhi-Wei
authors: ZW
authors: Shan
authors: Ju
authors: J
authors: Li
authors: Jun
authors: J
authors: Sun
authors: Evan
authors: E
authors: Ma