scholarly journals Controlling shear band instability by nanoscale heterogeneities in metallic nanoglasses

2021 ◽  
Author(s):  
Sree Harsha Nandam ◽  
Ruth Schwaiger ◽  
Aaron Kobler ◽  
Christian Kübel ◽  
Chaomin Wang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Yield Strength ◽  
Shear Band ◽  
Metallic Glasses ◽  
Strain Localization ◽  
Catastrophic Failure ◽  
Compression Tests ◽  
Medium Range ◽  
Shear Transformation ◽  
Shear Transformation Zones

Abstract Strain localization during plastic deformation drastically reduces the shear band stability in metallic glasses, ultimately leading to catastrophic failure. Therefore, improving the plasticity of metallic glasses has been a long-standing goal for several decades. In this regard, nanoglass, a novel type of metallic glass, has been proposed to exhibit differences in short and medium range order at the interfacial regions, which could promote the formation of shear transformation zones. In the present work, by introducing heterogeneities at the nanoscale, both crystalline and amorphous, significant improvements in plasticity are realized in micro-compression tests. Both amorphous and crystalline dispersions resulted in smaller strain bursts during plastic deformation. The yield strength is found to increase significantly in Cu–Zr nanoglasses compared to the corresponding conventional metallic glasses. The reasons for the mechanical behavior and the importance of nanoscale dispersions to tailor the properties is discussed in detail. Graphic Abstract

Stimulation of shear-transformation zones in metallic glasses by cryogenic thermal cycling

2020 ◽  
Vol 548 ◽  
pp. 120299 ◽  
Author(s):  
C.M. Meylan ◽  
F. Papparotto ◽  
S. Nachum ◽  
J. Orava ◽  
M. Miglierini ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Metallic Glasses ◽  
Shear Transformation ◽  
Shear Transformation Zones ◽  
Stimulation Of

Shear Band Feature in Two Bulk Metallic Glasses with Different Inherent Plasticity

2013 ◽  
Vol 703 ◽  
pp. 20-23
Author(s):  
Jian Sheng Gu ◽  
Hui Feng Bo ◽  
Hong Li ◽  
Zhan Xin Zhang
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Temperature Rise ◽  
Metallic Glasses ◽  
Shear Banding ◽  
Shear Bands ◽  
Significant Difference ◽  
Coating Method ◽  
Deformation Ability

Shear banding characterization of Zr64.13Cu15.75Ni10.12Al10 and Zr65Cu15Ni10Al10 BMGs was studied by using Rockwell indention method. The significant difference in plastic deformation ability can be ascribed to different shear banding features. Meanwhile, by using the fusible coating method, thermal effect on shear bands was investigated. We did not see apparently temperature rise in shear bands of these two BMGs through Rockwell indentation.

Localized heating and fracture criterion for bulk metallic glasses

2006 ◽  
Vol 21 (4) ◽  
pp. 915-922 ◽  
Author(s):  
B. Yang ◽  
C.T. Liu ◽  
T.G. Nieh ◽  
M.L. Morrison ◽  
P.K. Liaw ◽  
...  
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Zone Model ◽  
Transformation Zone ◽  
Localized Heating ◽  
Instantaneous Temperature ◽  
Shear Transformation ◽  
New Criterion

In this study, we demonstrated that the failure of bulk metallic glasses (BMGs) results from a sudden temperature rise within a shear band. Using a shear transformation zone model, we successfully calculated the temperature within a shear band and found it consistent with the observation from an in situ infrared thermographic system. The instantaneous temperature within a shear band at fracture agrees remarkably well with the glass transition temperature (Tg providing a new criterion to determine the strength of BMGs from their Tg. This agreement also discloses the fact that catastrophic failure of BMG is caused by the sudden drop in viscosity inside the shear band when the instantaneous temperature within a shear band approaches Tg.

Single sample method for assessing the Baushinger effect

2020 ◽  
Vol 86 (7) ◽  
pp. 55-58
Author(s):  
A. D. Khvan ◽  
D. V. Khvan ◽  
A. A. Voropaev
Keyword(s):  
Plastic Deformation ◽  
Stress State ◽  
Yield Strength ◽  
Bauschinger Effect ◽  
Calculated Data ◽  
Compressive Yield Strength ◽  
Special Device ◽  
Compression Tests ◽  
Traditional Procedure

The Bauschinger effect is one of the fundamental properties of most metal alloys exposed to plastic deformation under non-monotonic loading. Development of the methods for quantifying this effect is one the important issues of the theory of plasticity. Calculation of the parameter characterizing the aforementioned effect is required for determination of the stress state in plastically deformable blanks upon pressure metal treatment. The value of the parameter (determined in standard tensile tests followed by subsequent compression of samples) is defined by the ratio of the conditional yield strength of the sample under compression to the value of the preliminary tensile stress. A series of cylindrical samples (~10 pcs.) is usually taken for tensile-compression tests. According to the traditional procedure, long-size standard specimens are pre-stretched to various degrees of plastic deformation. After that short specimens are cut out from those specimens for compression tests to determine the conditional compressive yield strength with a tolerance of 0.2% for plastic deformation. Such a procedure is rather time consuming and expensive. We propose and develop a new single-model method for estimating the Bauschinger effect which consists in testing of a single long-size specimen for tension followed by compression of the specimen in a special device providing deformation of a previously stretched specimen without flexure under conditions of a linear stress state. The device was designed, manufactured and underwent the appropriate tests. The device contains supporting elements in the form of conical-shaped sectors that prevent flexure of a long cylindrical specimen upon compression, a ratio of the working part length to diameter ranges from 5 to 10. The results of experimental determination of the parameter β characterizing the indicated effect are presented. The results of comparing the values of the parameter β determined by the developed and traditional methods revealed the possibility of determining the parameter β using the proposed method. To reduce the complexity of performing tests related to determination of the parameter β we approximated it in the form of an exponent as a function of the magnitude of plastic deformation and determine the only one value of β0 under plastic deformations exceeding 0.05. In this regard, β0 can be considered a new characteristic of the material. The calculated data are in good agreement with the experimental results. The values of β0 are determined for a number of studied steel grades.

scholarly journals Probe Embryonic Damage Evolution in Bulk Metallic Glasses under Plate-impact Loading

2018 ◽  
Vol 183 ◽  
pp. 03013
Author(s):  
Zhong Ling ◽  
Xin Huang ◽  
Lanhong Dai
Keyword(s):  
Metallic Glass ◽  
Metallic Glasses ◽  
Volume Content ◽  
Impact Loading ◽  
Damage Evolution ◽  
Ductile Damage ◽  
Plate Impact ◽  
Shear Transformation ◽  
Stress Environment ◽  
Shear Transformation Zones

Microdamage in very short stress durations of spallation process in Zr-based bulk metallic glass (Zr-BMG) samples were captured by a specially designed plate impact technique. With stress durations vary, microdamage “frozen” in Zr-BMG samples exhibited different damage levels. Based on the morphology and stress environment of the microdamage, a compound microdamage evolution mode is applied to characterize the spallation evolution in Zr-BMGs. Especially the spallation in BMGs originates from cavitation instabilities in the weak regions with higher free volume content, which results in formation of ductile damage zones. The activation of shear transformation zones (STZs) or tension transformation zones (TTZs) between these ductile damage zones finally leads to detached spallation.

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