Effects of changes in strain rate and test temperature on Mg85Ca5Cu10 metallic glass ribbons

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.

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Strain-rate effect on yielding behavior of an in-situ Ti-based metallic glass matrix composite upon dynamic compression

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141267 ◽

2021 ◽

Vol 815 ◽

pp. 141267

Author(s):

Kuo Li ◽

Zhiming Jiao ◽

Zhiqiang Li ◽

Zhihua Wang

Keyword(s):

Metallic Glass ◽

Strain Rate ◽

Matrix Composite ◽

Glass Matrix ◽

Dynamic Compression ◽

Strain Rate Effect ◽

Glass Matrix Composite ◽

Yielding Behavior ◽

Metallic Glass Matrix Composite

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Flow Stress and Elongation of Superplastic Deformation in La55Al25Ni20 Metallic Glass

MRS Proceedings ◽

10.1557/proc-601-303 ◽

1999 ◽

Vol 601 ◽

Author(s):

Y. Kawamura ◽

A. Inoue

Keyword(s):

Flow Stress ◽

Metallic Glass ◽

Strain Rate ◽

Superplastic Deformation ◽

Constant Strain Rate ◽

Supercooled Liquid ◽

Supercooled Liquid Region ◽

Liquid Region ◽

Elongation To Failure ◽

Crosshead Velocity

AbstractWe have investigated the flow stress and elongation of superplastic deformation in a La55Al25Ni20 (at%) metallic glass that has a wide supercooled liquid region of 72 K before crystallization. The superplasticity that appeared in the supercooled liquid region was generated by the Newtonian viscous flow that exhibits the m value of unity. The elongation to failure was restricted by the transition of the Newtonian flow to non-Newtonian one and the crystallization during deformation. We succeeded in establishing the constitutive formulation of the flow stress in the supercooled liquid region. Its formulation was expressed very well by a stretched exponential function σflow=Dε exp(H*/RT) [1-exp(E/{ε exp(H**/RT)}0.82)]. Formulations describing the elongation to failure in constant-strain-rate and constant-crosshead velocity tests were, moreover, established. It was found from the simulation that the maximum elongation in the constant-strain-rate test reached more than 106% which was two orders of magnitude larger than that in the constant-crosshead-velocity test.

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Strain-rate dependence of hardening and softening in compression of a bulk-metallic glass

Journal of Materials Research ◽

10.1557/jmr.2007.0351 ◽

2007 ◽

Vol 22 (10) ◽

pp. 2655-2658 ◽

Cited By ~ 11

Author(s):

W.H. Jiang ◽

F.X. Liu ◽

F. Jiang ◽

K.Q. Qiu ◽

H. Choo ◽

...

Keyword(s):

Flow Stress ◽

Metallic Glass ◽

Strain Rate ◽

Bulk Metallic Glass ◽

Plastic Flow ◽

Shear Banding ◽

Constant Strain Rate ◽

Rate Dependence ◽

Strain Rate Dependence ◽

Plastic Flow Stress

We investigated the effect of strain rate on the plastic-flow stress of a Zr-based bulk-metallic glass in quasistatic compression. The results indicate that the plastic-flow stress is dependent on the strain rate: an increase in the strain rate leads to a decrease in the plastic-flow stress, and vice versa. However, simply loading, unloading, and reloading at a constant strain rate do not change the plastic-flow stress. This strain-rate dependence of the plastic-flow stress may be related to shear-banding operations.

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