Microstructure and Stability of Metallic Nanoglasses

• Applicants: Professor Dr. Karsten Albe; Professor Dr.-Ing. Horst Hahn
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Glass, Ceramics and Derived Composites ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: from 2006 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 30799144

• Final Report Year: 2019

Final Report Abstract

The microstructural model developed in this project from both experimental and simulation studies can be described as follows: Atoms in the cores of the nanoglass and interfacial regions can show distinct SRO and MRO, but no long range order. Thus, the entire material remains fully amorphous, however, with distinct structural differences between the cores and the interfaces. Due to the extra free volume created during the compaction of the amorphous nanoparticles and segregation effects, the amorphous structure can relax into an energetically more favorable structure, but without undergoing crystallization. This finding is in sharp contrast to the structural arrangement typical of crystalline materials. For the crystalline case, the introduction of interfaces (grain boundaries) results in a reduction of order accompanied by an increase of the free energy of the system. By contrast, in an amorphous, disordered material system, the introduction of ’‘defects” (interfaces, free volume, compositional variation) allows the amorphous structure to relax into a structure with an increased order and a lower free energy depending on the material system. This new amorphous structure, in between that of the RQ state and the crystalline order, is only possible under the special synthesis conditions used for nanoglasses. Our research provides evidence that such a state of an amorphous structure can at this point in time only be obtained by compaction of amorphous nanoparticles, i.e., when all processing steps are performed in the solid state. The processes occurring during compaction at room temperature are different from rapid quenching, when the structure of the molten state (which is entropy stabilized) is frozen due to the rapid cooling process, which does not allow the relaxation into lower energetic states. The structure of nanoglasses gives rise to a range of different mechanical, thermal, and magnetic properties of nanoglasses compared to those of the RQ ribbons with the same chemical compositions. In summary, nanoglasses represent a new and interesting family of amorphous materials that are distinctly different from RQ metallic glasses. Thus, these materials open up the opportunity for potential use in a number of structural and functional applications.

Publications

• Evidence for Enhanced Ferromagnetism in an Iron-Based Nanoglass, Appl. Phys. Lett. 103 (7) (2013) 4818493
  R. Witte, T. Feng, J. X. Fang, A. Fischer, M. Ghafari, R. Kruk, R. A. Brand, D. Wang, H. Hahn, H. Gleiter
  
• Influence of Grain Size and Composition, Topology and Excess Free Volume on the Deformation Behavior of Cu-Zr Nanoglasses, Beilstein J. of Nanotechnology 6 (2015) 537–545
  D. Sopu, K. Albe
  
• Generating Metallic Amorphous Core-Shell Nanoparticles by a Solid-State Amorphization Process, Particle & Particle System Characterization 33 (2) (2016) 82–88
  T. Feng, D. Wang, C. Wang, N. Chen, H. Hahn, H. Gleiter
  
• Interfaces and Interphases in Nanoglasses: Surface Segregation Effects and Their Implications on Structural Properties, Acta Mater. 113 (2016) 284–292
  O. Adjaoud, K. Albe
  
• Structural Origins of the Boson Peak in Metals: From High-Entropy Alloys to Metallic Glasses, Phys. Rev. B 94 (22) (2016) 224203
  T. Brink, L. Koch, K. Albe
  
• Investigation of the deposition conditions on the microstructure of TiZrCuPd nano-glass thin films, Mater. Charact. 131 (2017) 140–147
  M. Mohri, D. Wang, J. Ivanisenko, H. Gleiter, H. Hahn
  
• Microstructure formation of metallic nanoglasses: Insights from molecular dynamics simulations, Acta Mater. 145 (2018) 322–330
  O. Adjaoud, K. Albe
  
• Structure and Properties of Nanoglasses, Adv. Eng. Mater. 20 (12) (2018) 1800404
  Y. Ivanisenko, C. Kübel, O. Adjaoud, S. H. Nandam, C. Wang, X. Mu, K. Albe, H. Hahn
  
• Thermal stability of the Ti-Zr-Cu-Pd nanoglassy thin films, J. Alloys Compd. 735 (2018) 2197–2204
  M. Mohri, D. Wang, J. Ivanisenko, H. Gleiter, H. Hahn