Non-octahedral-like dislocation glides in aluminum induced by athermal effect of electric pulse
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an Wang and Wenjun Zhu National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, Sichuan, People’s Republic of China
Chaoying Xie State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China; and Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China (Received 1 January 2016; accepted 25 February 2016)
The dislocation movements under the action of electric pulses (athermal effect) at cryogenic conditions were studied by ex situ transmission electron microscopy (TEM) observations and slip trace analysis innovatively. By applying electric pulses directly through aluminum TEM samples in a liquid nitrogen bath, plenty of non-octahedral-like dislocation glides generally forming at high temperatures (e.g., .453 K for aluminum) were observed at cryogenic temperatures (,130 K). Occurrence of the non-octahedral-like dislocation glides indicates a substantial increase in the degrees of freedom for dislocation glides, offering a new/ complementary explanation for the acceleration effect of electric pulses on dislocation movements, especially in the sole athermal effect. In comparison, previous theories relied on extra driving force and/or increased dislocation mobility on the octahedral planes in a face-centered cubic metal. The athermal effects of electric pulse were discussed and the selective heating at the dislocation cores was proposed to account for non-octahedral-like dislocation glides.
I. INTRODUCTION
It is well known that intense electric pulses can significantly accelerate the dislocation movements, and thereby lead to a rapid recovery and recrystallization1,2 or reduce the flow stress and increase the plasticity of metals undergoing plastic deformation (often referred to as electroplasticity).3–8 Based on the electroplasticity, a variety of electropulse-assisted processing techniques have already been developed and demonstrated to be highly-effective and highly-efficient for various metallic materials such as aluminum, stainless steel [face-centered cubic (f.c.c)],5,9 low carbon steel [bodycentered cubic (b.c.c)],9 magnesium,7,10 and titanium [hexagonal close-packed (h.c.p)]11,12 and so on. The acceleration effect on dislocation movement was first experimentally discovered by Troitskii and Likhtman in 1963 (Ref. 13) and thereafter two categories of Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.90
mechanisms were proposed in the subsequent decades. The first category of mechanism for the acceleration effect was based on the concept of direct interaction between drifting electrons and dislocations.13–18 The basic idea is that, the drifting electrons can exert a stress (called “electron wind”) on dislocations and also enhance the mobility o
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