Instability Analysis and Free Volume Simulations of Shear Band Directions and Arrangements in Notched Metallic Glasses

As a commonly used method to enhance the ductility in bulk metallic glasses (BMGs), the introduction of geometric constraints blocks and confines the propagation of the shear bands, reduces the degree of plastic strain on each shear band so that the catastrophic failure is prevented or delayed, and promotes the formation of multiple shear bands. The clustering of multiple shear bands near notches is often interpreted as the reason for improved ductility. Experimental works on the shear band arrangements in notched metallic glasses have been extensively carried out, but a systematic theoretical study is lacking. Using instability theory that predicts the onset of strain localization and the free-volume-based finite element simulations that predict the evolution of shear bands, this work reveals various categories of shear band arrangements in double edge notched BMGs with respect to the mode mixity of the applied stress fields. A mechanistic explanation is thus provided to a number of related experiments and especially the correlation between various types of shear bands and the stress state.

[1]  Yanfei Gao,et al.  On the correlation between microscopic structural heterogeneity and embrittlement behavior in metallic glasses , 2015, Scientific Reports.

[2]  Yujie Wei,et al.  Notch strengthening or weakening governed by transition of shear failure to normal mode fracture , 2015, Scientific Reports.

[3]  Joško Ožbolt,et al.  Numerical study of mixed-mode fracture in concrete , 2002 .

[4]  Yanfei Gao,et al.  Thin-film metallic glasses for substrate fatigue-property improvements , 2014 .

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

[6]  Bingchen Wei,et al.  Initiation and propagation of shear bands in Zr-based bulk metallic glass under quasi-static and dynamic shear loadings , 2005 .

[7]  Yanfei Gao,et al.  On the shear-band direction in metallic glasses , 2011 .

[8]  Huajian Gao,et al.  Origin of anomalous inverse notch effect in bulk metallic glasses , 2015 .

[9]  Y. Gao,et al.  An implicit finite element method for simulating inhomogeneous deformation and shear bands of amorphous alloys based on the free-volume model , 2006 .

[10]  Mariana Calin,et al.  Metallic glasses: Notch-insensitive materials , 2012 .

[11]  H. Bei,et al.  Controlled normal/shear loading and shear fracture in bulk metallic glasses , 2009 .

[12]  Reinhold H. Dauskardt,et al.  Mean stress effects on flow localization and failure in a bulk metallic glass , 2001 .

[13]  Jiaxi Zhao,et al.  Plastic deformability of metallic glass by artificial macroscopic notches , 2010 .

[14]  Yanfei Gao,et al.  Intergranular strain evolution near fatigue crack tips in polycrystalline metals , 2011 .

[15]  Yong-Wei Zhang,et al.  Cavitation in brittle metallic glasses – Effects of stress state and distributed weak zones , 2014 .

[16]  Huajian Gao,et al.  Cavitation in materials with distributed weak zones: Implications on the origin of brittle fracture in metallic glasses , 2013 .

[17]  P. Liaw,et al.  Interface Constraints on Shear Band Patterns in Bonded Metallic Glass Films Under Microindentation , 2012, Metallurgical and Materials Transactions A.

[18]  C. Schuh,et al.  Densification and strain hardening of a metallic glass under tension at room temperature. , 2013, Physical review letters.

[19]  John W. Hutchinson,et al.  Strain localization in amorphous metals , 1982 .

[20]  Jiaxi Zhao,et al.  Comparison of compressive deformation and fracture behaviors of Zr- and Ti-based metallic glasses with notches , 2011 .

[21]  Z. Suo,et al.  Notch-sensitivity and shear bands in brittle matrix composites , 1994 .

[22]  Yanfei Gao,et al.  Deformation-induced spatiotemporal fluctuation, evolution and localization of strain fields in a bulk metallic glass , 2015 .

[23]  U. Ramamurty,et al.  Mixed mode (I and II) crack tip fields in bulk metallic glasses , 2009 .

[24]  T. Nieh,et al.  Flow serration in a Zr-based bulk metallic glass in compression at low strain rates , 2008 .

[25]  H. Bei,et al.  Shear fracture of bulk metallic glasses with controlled applied normal stresses , 2008 .

[26]  Yanfei Gao,et al.  Structural heterogeneity induced plasticity in bulk metallic glasses: From well-relaxed fragile glass to metal-like behavior , 2013 .

[27]  J. Schroers,et al.  Designing tensile ductility in metallic glasses , 2013, Nature Communications.

[28]  U. Ramamurty,et al.  On the mechanism and the length scales involved in the ductile fracture of a bulk metallic glass , 2013 .

[29]  L. Dai,et al.  Nature of crack-tip plastic zone in metallic glasses , 2016 .

[30]  J. Rice,et al.  CONDITIONS FOR THE LOCALIZATION OF DEFORMATION IN PRESSURE-SENSITIVE DILATANT MATERIALS , 1975 .

[31]  Mihai Stoica,et al.  Mechanical and Structural Investigation of Porous Bulk Metallic Glasses , 2015 .

[32]  J. C. Huang,et al.  Is the compression of tapered micro- and nanopillar samples a legitimate technique for the identification of deformation mode change in metallic glasses? , 2012 .