Tailoring plasticity of metallic glasses via interfaces in Cu/amorphous CuNb laminates
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Qiang Li School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
Jin Li Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77843-3003, USA
Sichuang Xue Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843-3123, USA
Haiyan Wang School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA; and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
Xinghang Zhangb) School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA (Received 23 March 2017; accepted 31 May 2017)
Metallic glasses (MGs) are known to have high strength, but poor ductility. Prior studies have shown that plasticity in MG can be enhanced by significantly reducing their dimension to nanoscale. Here we show that, via the introduction of certain types of crystalline/amorphous interfaces, plasticity of MG can be prominently enhanced as manifested by the formation of ductile “dimples” in a 2 lm thick amorphous CuNb film. By tailoring the volume fraction and architecture of crystalline/amorphous multilayers, tensile fracture surface of MG can evolve from brittle featureless morphology to containing ductile dimples. In situ micropillar compression studies performed inside a scanning electron microscope show that shear instability in amorphous layers can be inhibited by interfaces. The mechanisms for improving plasticity and fracture resistance of MG via interface and size effect are discussed.
I. INTRODUCTION
Metallic glasses (MGs) exhibit high yield strength, large elastic strain, and excellent wear resistance,1–3 but show limited plasticity and often fail catastrophically by forming shear bands especially under tension.4–6 The incorporation of crystalline phases into MGs can hinder the propagation of shear bands and promote the formation and multiplication of shear bands, and thus increase the ductility of metallic glass composites (MGc).7–11 The tensile ductility of ZrTi-based bulk metallic glass composites (BMGc) can exceed 10% strain by the introduction of crystalline dendrites.12 The motif of adding ductile crystalline phases into MGs to enhance ductility also works for thin film metallic glass composites (TFMGc).13–19 For instance, Cu 35 nm/amorphous CuZr 5 nm multilayer film can attain ;14% tensile ductility.20
Contributing Editor: Jürgen Eckert Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2017.249
The constraint induced by crystalline phases on MGs can enhance plasticity of MGs under tension,17,20 compression,14,21 or bending,15 but the effects of volume fraction of crystalline phase on fracture behaviors of MGs under tension are less well understood especially at nanoscale. Meanwhile micropillar compression tests are proved to be a suitable method to study the deformation behaviors of MGs.22–26 Compression results show that the yield strength of MGs increase
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