Mechanism of negative strain rate sensitivity in metallic glass film

2019 ◽  
Vol 784 ◽  
pp. 488-499 ◽  
Author(s):  
Bibhu Prasad Sahu ◽  
Amlan Dutta ◽  
Rahul Mitra
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Glass Film ◽  
Negative Strain Rate Sensitivity

scholarly journals Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 339
Author(s):  
Xiang Wang ◽  
Zhi Qiang Ren ◽  
Wei Xiong ◽  
Si Nan Liu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Strain Rate Sensitivity ◽  
Critical Role ◽  
Rate Sensitivity ◽  
Confined Compression ◽  
Negative Strain Rate Sensitivity ◽  
Cast Specimen ◽  
Structure Heterogeneity

The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.

Stress-State, Temperature, and Strain Rate Dependence of Vintage ASTM A7 Steel

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
S. A. Brauer ◽  
W. R. Whittington ◽  
H. Rhee ◽  
P. G. Allison ◽  
D. E. Dickel ◽  
...  
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Rate Dependence ◽  
Maximum Strength ◽  
Strain Rate Dependence ◽  
Dynamic Strain ◽  
Strength Increase ◽  
Negative Strain Rate Sensitivity

The structure–property relationships of a vintage ASTM A7 steel is quantified in terms of stress state, temperature, and strain rate dependence. The microstructural stereology revealed primary phases to be 15.8% ± 2.6% pearlitic and 84.2% ± 2.6 ferritic with grain sizes of 13.3 μm ± 3.1 μm and 36.5 μm ± 7.0 μm, respectively. Manganese particle volume fractions represented 0.38–1.53% of the bulk material. Mechanical testing revealed a stress state dependence that showed a maximum strength increase of 85% from torsion to tension and a strain rate dependence that showed a maximum strength increase of 38% from 10−1 to 103 s−1at 20% strain. In tension, a negative strain rate sensitivity (nSRS) was observed in the quasi-static rate regime yet was positive when traversing from the quasi-static rates to high strain rates. Also, the A7 steel exhibited a significant ductility reduction as the temperature increased from ambient to 573 K (300 °C), which is uncommon for metals. The literature argues that dynamic strain aging (DSA) can induce the negative strain rate sensitivity and ductility reduction upon a temperature increase. Finally, a tension/compression stress asymmetry arises in this A7 steel, which can play a significant role since bending is prevalent in this ubiquitous structural material. Torsional softening was also observed for this A7 steel.

Tuning the strain rate sensitivity and ductility of Zr55Al10Cu30Ni5 metallic glass by He+ ion irradiation

2020 ◽  
Vol 840 ◽  
pp. 155562
Author(s):  
Huaican Chen ◽  
Yang Hai ◽  
Gang Wang ◽  
Xiao Liu ◽  
Juping Xu ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Ion Irradiation ◽  
Rate Sensitivity

Negative strain rate sensitivity in ultrahigh-strength nanocrystalline tantalum

2006 ◽  
Vol 89 (8) ◽  
pp. 081903 ◽  
Author(s):  
Y. M. Wang ◽  
A. M. Hodge ◽  
P. M. Bythrow ◽  
T. W. Barbee ◽  
A. V. Hamza
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Negative Strain Rate Sensitivity ◽  
Ultrahigh Strength
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