Atomistic scale modeling of metallic glass-based hybrid composites with tailored design

• Applicant: Daniel Sopu, Ph.D.
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Theoretical Condensed Matter Physics
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318962047

• Final Report Year: 2020

Final Report Abstract

All objectives of the project were attained. The main achievements are presented in the following. Towards the edge of plasticity in heterostructures with smart nanoarchitectures: • A new atomic-level mechanism underlying the shear banding process in monolithic metallic glasses was proposed. This mechanism is based on the autocatalytic generation of successive strong strain (corresponding to STZs) and rotation (vortex-like units) fields, leading to the consecutive activation of STZs and, ultimately, to the formation of a shear band. • The fundamental characteristics of shear band branching and multiplication mechanisms were highlighted based on the new STZ-vortex unit. Deformation chain reaction in shape memory BMG composites: • Tailoring the architecture of MG composites with shape memory phases can allow the development of materials that exhibit large tensile ductility. • The deformation of the glassy and crystalline phases is a coupled process: martensitic transformation leads to shear band formation while the stress at the shear band tip induces martensitic transformation in the shape memory crystal. • MG nanolaminates with B2 layer show a competing deformation mechanism between martensitic transformation and shear band propagation. • MG laminar composites with a low volume fraction of B2 layers experience enhanced tensile ductility and nearly ideal plastic flow behavior. Structure-property relationships: • By tuning the density of crystalline precipitates, their distribution and size together with intrinsic properties of the phase one can control the brittle-to-ductile transition in the MG composites. • Shape memory inclusions are more efficient in improving the deformation behaviors of MG composites as compared to the soft nanocrystalline inclusions which deform via dislocation activity. • A low density of small shape memory inclusions with spacing smaller than the critical shear band length controls the formation and distribution of plastic zones in the composite and hinders the formation of critical shear bands. Tuning mechanical properties by iterative deformation: • Besides the previous presented beneficial effects for improving the deformability of MG composites, the cyclic loading in the elastic regime can improve even more their mechanical properties. • Tensile loading cycles on MG composites rejuvenated the glassy matrix that enhance their ductility and increases the yield strength.

Publications

• ”Atomic-level processes of shear band nucleation in metallic glasses.” Physical Review Letters 119, no. 19 (2017): 195503
  D. Şopu, A. Stukowski, M. Stoica, S. Scudino
  
• ”Bond length deviation in CuZr metallic glasses.” Physical Review B 96, no. 17 (2017): 174112
  CX. Peng, D. Şopu, KK. Song, ZT. Zhang, L. Wang, J. Eckert
  
• ”Metallic glass nanolaminates with shape memory alloys.” Acta Materialia 159 (2018): 344-351
  D. Şopu, K. Albe, J. Eckert
  
• ”Strain distribution across an individual shear band in real and simulated metallic glasses.” Nano Letters 18, no. 2 (2018): 1221-1227
  S. Scudino, D. Şopu
  
• ”Deformation behavior of designed dual-phase CuZr metallic glasses.” Materials Design 168 (2019): 107662
  CX. Peng, D. Sopu, Y. Cheng, KK. Song, SH. Wang, J. Eckert, L. Wang
  
• ”Modulating heterogeneity and plasticity in bulk metallic glasses: Role of interfaces on shear banding.” International Journal of Plasticity 119 (2019): 156-170
  K. Kosiba, D. Sopu S Scudino, L. Zhang, J. Bednarcik, S. Pauly
  
• ”Structure-Property Relationships in Shape Memory Metallic Glass Composites.” Materials 12, no. 9 (2019): 1419
  D. Sopu, X. Yuan, F. Moitzi, M. Stoica, J. Eckert
  
• ”Atomic-scale origin of shear band multiplication in heterogeneous metallic glasses.” Scripta Materialia 178 (2020): 57-61
  D. Sopu, S. Scudino, XL. Bian, C. Gammer, J. Eckert
  
• ”Chemical bonding effects on the brittle-to-ductile transition in metallic glasses.” Acta Materialia 188 (2020): 273-281
  F. Moitzi, D. Sopu, D. Holec, D. Perera, N. Mousseau, J. Eckert