Structural processes that initiate shear localization in metallic glass

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.

[1]  Yueguang Wei,et al.  Atomistic simulations of crack nucleation and intergranular fracture in bulk nanocrystalline nickel , 2007 .

[2]  E. Ma,et al.  Local order influences initiation of plastic flow in metallic glass: Effects of alloy composition and sample cooling history , 2008 .

[3]  Ju Li,et al.  Yield point of metallic glass , 2006 .

[4]  T. Hufnagel,et al.  Mechanical behavior of amorphous alloys , 2007 .

[5]  Mo Li,et al.  Atomic scale characterization of shear bands in an amorphous metal , 2006 .

[6]  M. Denda,et al.  Dynamic evolution of nanoscale shear bands in a bulk-metallic glass , 2005 .

[7]  Ju Li,et al.  Theory of Shear Banding in Metallic Glasses and Molecular Dynamics Calculations , 2007 .

[8]  Weighted Voronoi tessellation technique for internal structure of metallic glasses , 2007 .

[9]  Christopher A. Schuh,et al.  Initiation of shear bands near a stress concentration in metallic glass , 2007 .

[10]  David A. Weitz,et al.  Structural Rearrangements That Govern Flow in Colloidal Glasses , 2007, Science.

[11]  Evan Ma,et al.  Relationship between structure, dynamics, and mechanical properties in metallic glass-forming alloys , 2008 .

[12]  E. Ma,et al.  Atomic level structure in multicomponent bulk metallic glass. , 2009, Physical review letters.

[13]  J. Langer,et al.  Dynamics of viscoplastic deformation in amorphous solids , 1997, cond-mat/9712114.

[14]  Frans Spaepen,et al.  A microscopic mechanism for steady state inhomogeneous flow in metallic glasses , 1977 .

[15]  A. Argon.  Plastic deformation in metallic glasses , 1979 .

[16]  J. H. He,et al.  Icosahedral short-range order in amorphous alloys. , 2004, Physical review letters.

[17]  W. Johnson,et al.  A universal criterion for plastic yielding of metallic glasses with a (T/Tg) 2/3 temperature dependence. , 2005, Physical review letters.

[18]  E. Ma,et al.  Correlation between the elastic modulus and the intrinsic plastic behavior of metallic glasses: The roles of atomic configuration and alloy composition , 2009 .

[19]  A. L. Greer,et al.  Bulk Metallic Glasses: At the Cutting Edge of Metals Research , 2007 .

[20]  Mingwei Chen,et al.  Experimental characterization of shear transformation zones for plastic flow of bulk metallic glasses , 2008, Proceedings of the National Academy of Sciences.

[21]  K. Jacobsen,et al.  Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses , 2006 .

[22]  J. Bai,et al.  Atomic packing and short-to-medium-range order in metallic glasses , 2006, Nature.

[23]  J. D. Eshelby.  The determination of the elastic field of an ellipsoidal inclusion, and related problems , 1957, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[24]  Strain localization and percolation of stable structure in amorphous solids. , 2005, Physical review letters.