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[资源] 【原创】Structural processes that initiate shear localization in metallic glass

Structural processes that initiate shear localization in metallic glass

A.J. Cao, a, , Y.Q. Chenga and E. Maa,

aDepartment of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA

Received 5 May 2009; revised 9 July 2009; accepted 9 July 2009. Available online 7 August 2009.

Abstract
For crystalline metals, the structural carriers (dislocations and twins) of plasticity have been well characterized. In contrast, the structural processes responsible for the localized shear flow in amorphous metals remain poorly understood. Using molecular dynamics simulations, we illustrate here how the shear localization initiates in a Cu–Zr metallic glass. We identify the breakdown of full icosahedral clusters as a structural signature of the initiation of shear localization, which is demonstrated to be a spontaneous and autocatalytic instability propagating with a velocity close to the speed of sound. Structural disorder induced softening precedes thermal softening as the origin of the shear banding. Once the deformation band penetrates across the entire sample, the already-rejuvenated structure inside allows the entire band to collectively slip as a whole, to grow the shear offsets on both sides of the sample.

Keywords: Bulk metallic glass; Shear localization; Mechanical properties; Instability; Shear transformation

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