Nucleation of shear bands in amorphous alloys

Significance A shear band is a region of highly localized plastic flow that develops during loading in both crystalline and amorphous materials. Shear bands directly determine the ductility of an amorphous phase, but relatively little is known about their nucleation. We use nanoindentation to probe shear band nucleation by measuring the first pop-in event during loading which is associated with shear band formation. We analyze a large number of independent measurements on four different metallic glasses and reveal a bimodal distribution of nucleation events that operate at different stress levels. The discovery of multiple shear band nucleation sites challenges the current view of a single type of site and offers opportunities for controlling the ductility of amorphous alloys. The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load–depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys.

[1]  Hongkai Wu,et al.  Ductile Biodegradable Mg‐Based Metallic Glasses with Excellent Biocompatibility , 2013 .

[2]  Evan Ma,et al.  Shear bands in metallic glasses , 2013 .

[3]  M. Fu,et al.  Investigation on the inhomogeneous structure of metallic glasses based on the initial elastic deformation in nanoindentation , 2012 .

[4]  T. Nieh,et al.  Direct measurements of shear band propagation in metallic glasses – An overview , 2011 .

[5]  T. Nieh,et al.  Onset of yielding and shear band nucleation in an Au-based bulk metallic glass , 2011 .

[6]  A. Vinogradov,et al.  Probing shear-band initiation in metallic glasses. , 2011, Physical review letters.

[7]  Julia R. Greer,et al.  Plasticity in small-sized metallic systems: Intrinsic versus extrinsic size effect , 2011 .

[8]  W. Arnold,et al.  Local elastic properties of a metallic glass. , 2011, Nature materials.

[9]  J. Hosson,et al.  Intrinsic size effects in the mechanical response of taper-free nanopillars of metallic glass , 2011 .

[10]  A. Nwankpa,et al.  An atomically quantized hierarchy of shear transformation zones in a metallic glass , 2011 .

[11]  Wei Zhang,et al.  Characterization of nanoscale mechanical heterogeneity in a metallic glass by dynamic force microscopy. , 2011, Physical review letters.

[12]  I. Todd,et al.  A study of mechanical homogeneity in as-cast bulk metallic glass by nanoindentation , 2011 .

[13]  Robert O Ritchie,et al.  A damage-tolerant glass. , 2011, Nature materials.

[14]  Yequn Liu,et al.  Characterization of activation energy for flow in metallic glasses , 2011 .

[15]  Kwang-Ryeol Lee,et al.  Networked interpenetrating connections of icosahedra: Effects on shear transformations in metallic glass , 2011 .

[16]  C. Schuh,et al.  Three-dimensional shear transformation zone dynamics model for amorphous metals , 2010 .

[17]  A. Vinogradov.  On shear band velocity and the detectability of acoustic emission in metallic glasses , 2010 .

[18]  H. Bai,et al.  Relating activation of shear transformation zones to β relaxations in metallic glasses , 2010 .

[19]  A. Inoue,et al.  Energetic criterion on the intrinsic ductility of bulk metallic glasses , 2010 .

[20]  P. Schall,et al.  Shear Bands in Matter with Granularity , 2010 .

[21]  Evan Ma,et al.  Structural processes that initiate shear localization in metallic glass , 2009 .

[22]  C. Shek,et al.  Mechanical heterogeneity and mechanism of plasticity in metallic glasses , 2009 .

[23]  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.

[24]  Mingwei Chen,et al.  Mechanical Behavior of Metallic Glasses: Microscopic Understanding of Strength and Ductility , 2008 .

[25]  C. Volkert,et al.  Effect of sample size on deformation in amorphous metals , 2008 .

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

[27]  M. Demetriou,et al.  Anelastic to plastic transition in metallic glass-forming liquids. , 2007, Physical review letters.

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

[29]  Yunfeng Shi,et al.  Stress-induced structural transformation and shear banding during simulated nanoindentation of a metallic glass , 2007 .

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

[31]  A. L. Greer,et al.  Plasticity induced by nanoparticle dispersions in bulk metallic glasses , 2007 .

[32]  Wei Zhang,et al.  Measuring Elastic Energy Density of Bulk Metallic Glasses by Nanoindentation , 2006 .

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

[34]  Amy L. Rechenmacher,et al.  Grain-scale processes governing shear band initiation and evolution in sands , 2006 .

[35]  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.

[36]  H. Bei,et al.  Theoretical strength and the onset of plasticity in bulk metallic glasses investigated by nanoindentation with a spherical indenter. , 2004, Physical review letters.

[37]  D. Miracle,et al.  A structural model for metallic glasses , 2004, Microscopy and Microanalysis.

[38]  C. Schuh,et al.  Application of nucleation theory to the rate dependence of incipient plasticity during nanoindentation , 2004 .

[39]  Christopher A. Schuh,et al.  The transition from localized to homogeneous plasticity during nanoindentation of an amorphous metal , 2003 .

[40]  P. Bésuelle.  Compacting and dilating shear bands in porous rock: Theoretical and experimental conditions , 2001 .

[41]  A. Argon,et al.  Free energy spectra for inelastic deformation of five metallic glass alloys , 1980 .

[42]  A. Argon,et al.  Plastic flow in a disordered bubble raft (an analog of a metallic glass) , 1979 .

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

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

[45]  E. Gehan.  Estimating survival functions from the life table. , 1969, Journal of chronic diseases.