Improving the mechanical properties of Zr-based bulk metallic glass by controlling the activation energy for β-relaxation through plastic deformation
- Department of Mechanical Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580 (Japan)
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)
The mechanism of plastic deformation in bulk metallic glasses (BMGs) is widely believed to be based on a shear transformation zone (STZ). This model assumes that a shear-induced atomic rearrangement occurs at local clusters that are a few to hundreds of atoms in size. It was recently postulated that the potential energy barrier for STZ activation, W{sub STZ}, calculated using the cooperative shear model, is equivalent to the activation energy for β-relaxation, E{sub β}. This result suggested that the fundamental process for STZ activation is the mechanically activated β-relaxation. Since the E{sub β} value and the glass transition temperature T{sub g} of BMGs have a linear relation, that is, because E{sub β} ≈ 26RT{sub g}, the composition of the BMG determines the ease with which the STZ can be activated. Enthalpy relaxation experiments revealed that the BMG Zr{sub 50}Cu{sub 40}Al{sub 10} when deformed by high-pressure torsion (HPT) has a lower E{sub β} of 101 kJ/mol. The HPT-processed samples accordingly exhibited tensile plastic elongation (0.34%) and marked decreases in their yield strength (330 MPa). These results suggest that mechanically induced structural defects (i.e., the free volume and the anti-free volume) effectively act to reduce W{sub STZ} and increase the number of STZs activated during tensile testing to accommodate the plastic strain without requiring a change in the composition of the BMG. Thus, this study shows quantitatively that mechanically induced structural defects can overcome the compositional limitations of E{sub β} (or W{sub STZ}) and result in improvements in the mechanical properties of the BMG.
- OSTI ID:
- 22350794
- Journal Information:
- Applied Physics Letters, Vol. 105, Issue 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACTIVATION ENERGY
ALUMINIUM COMPOUNDS
COPPER COMPOUNDS
CRYSTAL DEFECTS
ELONGATION
ENTHALPY
GLASS
METALLIC GLASSES
PLASTICITY
PLASTICS
POTENTIAL ENERGY
RELAXATION
STRAINS
TRANSFORMATIONS
TRANSITION TEMPERATURE
YIELD STRENGTH
ZIRCONIUM COMPOUNDS