scholarly journals Testing Effects on Shear Transformation Zone Size of Metallic Glassy Films Under Nanoindentation

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 636 ◽  
Author(s):  
Yi Ma ◽  
Yuxuan Song ◽  
Xianwei Huang ◽  
Zhongli Chen ◽  
Taihua Zhang
Keyword(s):  
Metallic Glasses ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Creep Tests ◽  
Transformation Zone ◽  
Testing Effects ◽  
Loading Rates ◽  
Creep Flow ◽  
Shear Transformation ◽  
Shear Transformation Zone

Room-temperature creep tests are performed at the plastic regions of two different metallic glassy films under Berkovich nanoindetation. Relying on the strain rate sensitivity of the steady-state creep curve, shear transformation zone (STZ) size is estimated based on the cooperative shear model (CSM). By applying various indentation depths, loading rates, and holding times, the testing effects on the STZ size of metallic glasses are systematically studied. Experimental results indicate that STZ size is greatly increased with increased indentation depth and shortened holding time. Meanwhile, STZ size is weakly dependent on the loading history. Both the intrinsic and extrinsic reasons are discussed, to reveal the testing effects on the nanoindentation creep flow and STZ size.

scholarly journals On Mechanical Properties of Metallic Glass and its Liquid Vitrification Characteristics

2008 ◽  
Vol 41-42 ◽  
pp. 247-252
Author(s):  
Min Qiang Jiang ◽  
L.H. Dai
Keyword(s):  
Elastic Constants ◽  
Metallic Glasses ◽  
Critical Strain ◽  
Molar Mass ◽  
Characteristic Size ◽  
Transformation Zone ◽  
Shear Transformation ◽  
Shear Transformation Zone ◽  
Solid Glass ◽  
Characteristic Volume

A systematic survey of the available data such as elastic constants, density, molar mass, and glass transition temperature of 45 metallic glasses is conducted. It is found that a critical strain controlling the onset of plastic deformation is material-independent. However, the correlation between elastic constants of solid glass and vitrification characteristics of its liquid does not follow a simple linear relation, and a characteristic volume, viz. molar volume, maybe relating to the characteristic size of a shear transformation zone (STZ), should be involved.

scholarly journals Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

2011 ◽  
Vol 59 (5) ◽  
pp. 2057-2068 ◽  
Author(s):  
F. Jiang ◽  
M.Q. Jiang ◽  
H.F. Wang ◽  
Y.L. Zhao ◽  
L. He ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Transformation Zone ◽  
Brittle Transition ◽  
Shear Transformation ◽  
Shear Transformation Zone

The Thermal Shear-Transformation-Zone Theory: Homogeneous Flow and Superplasticity in Bulk Metallic Glasses

2003 ◽  
Vol 806 ◽  
Author(s):  
Michael L. Falk ◽  
James S. Langer ◽  
Leonid Pechenik
Keyword(s):  
Metallic Glass ◽  
Yield Stress ◽  
Metallic Glasses ◽  
Strain Rates ◽  
Superplastic Behavior ◽  
Transformation Zone ◽  
Transient Stress ◽  
Shear Transformation ◽  
Shear Transformation Zone ◽  
System Approaches

ABSTRACTWe present an extended version of our earlier shear-transformation-zone theory of amorphous plasticity that takes into account thermally assisted molecular rearrangements. As in the previous low-temperature theory a transition is predicted between jammed and flowing states at a well defined yield stress. In the new theory the jammed state below the yield stress exhibits thermally assisted creep. The theory accounts for the experimentally observed strain-rate dependence of the viscosity of a bulk metallic glass. In particular it models the onset of superplastic behavior at high strain rates as the system approaches the yield stress. The theory also captures many of the details of the transient stress-strrain response of the metallic glass at temperatures near the glass transition.

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