Positron-annihilation studies of free-volume changes in the bulk metallic glassZr65Al7.5Ni10Cu17.5during structural relaxation and at the glass transition

1999 ◽  
Vol 60 (13) ◽  
pp. 9212-9215 ◽  
Author(s):  
C. Nagel ◽  
K. Rätzke ◽  
E. Schmidtke ◽  
F. Faupel ◽  
W. Ulfert
Keyword(s):  
Glass Transition ◽  
Positron Annihilation ◽  
Free Volume ◽  
Structural Relaxation ◽  
Volume Changes

Free Volume Changes and Crack Tip Deformation in Bulk Metallic Glass Alloys and their Composites

2003 ◽  
Vol 806 ◽  
Author(s):  
Biraja P. Kanungo ◽  
Matthew J. Lambert ◽  
Katharine M. Flores
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Strain Localization ◽  
Shear Bands ◽  
Inhomogeneous Deformation ◽  
Volume Changes

ABSTRACTThe free volume changes associated with deformation of metallic glasses play an important role in strain localization in shear bands. However the details of these structural changes during inhomogeneous deformation are unclear. In this study, the free volume changes in Cu60Zr30Ti10 and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glasses were examined and quantified using differential scanning calorimetry following rolling and low temperature annealing. It was found that the height of the endothermic peak associated with the glass transition decreased following deformation whereas annealing resulted in an increase in the peak height. Additionally, the exothermic event associated with structural relaxation prior to the glass transition occurred at a lower temperature after rolling in the Zr-based system. Surprisingly, a similar shift in the onset temperature was not observed in the Cu-based system, suggesting a different structural relaxation mechanism. The Zr-based system was successfully modeled and the results indicated that the free volume increased ∼4% with inhomogeneous deformation and decreased ∼14% with annealing, consistent with expectations. In an effort to further characterize strain localization in shear bands, the development of a crack tip damage zone in a Zr-based bulk metallic glass composite was studied using scanning electron and atomic force microscopy. The first shear band developed at an angle of ∼60° from the crack propagation direction. This is discussed in light of the Mohr-Coulomb yield criterion for metallic glasses. The reinforcement phase arrested the growth of individual shear bands, while accumulated damage resulted in the shear bands cutting through the crystalline phase, ultimately resulting in crack branching and failure.

Positron Annihilation Lifetime Studies on Free Volume Changes in Polymers by CO2 Conditioning

1994 ◽  
Vol 175-178 ◽  
pp. 789-792 ◽  
Author(s):  
K. Tanaka ◽  
M. Ito ◽  
Hideki Kita ◽  
Katsutomo Okamoto ◽  
Yasuo Ito
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Lifetime Studies

Positron annihilation lifetime studies of free volume changes in polycarbonate under static tensile deformation

1992 ◽  
Vol 25 (9) ◽  
pp. 2407-2411 ◽  
Author(s):  
M. Y. Ruan ◽  
H. Moaddel ◽  
A. M. Jamieson ◽  
R. Simha ◽  
J. D. McGervey
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Tensile Deformation ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Static Tensile ◽  
Lifetime Studies

Relaxation Behavior of Zr-Cu-Al Ternary Bulk Glassy Alloy Studied by Using Positron Annihilation Techniques

2010 ◽  
Vol 654-656 ◽  
pp. 1070-1073 ◽  
Author(s):  
Akito Ishii ◽  
Shinya Mineno ◽  
Akihiro Iwase ◽  
Yokoyama Yoshihiko ◽  
Toyohiko J. Konno ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Isothermal Annealing ◽  
Glassy Alloy ◽  
Volume Ratio ◽  
Charpy Impact ◽  
Volume Changes ◽  
Appreciable Change ◽  
Positron Annihilation Lifetime ◽  
Bulk Glassy Alloy

Zr-based bulk glassy (BG) alloys show high tensile strength and a high Charpy impact value. In this study, the free volume changes for the hypoeutectic Zr60Cu30Al10 BG alloy during isothermal annealing below glass transition temperature (Tg) have been investigated by positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements. The positron lifetime of hypoeutectic and eutectic BG alloys is almost the same, although the atomic volume ratio, estimated by the density for the eutectic BG alloy is different from that for the hypoeutectic BG alloy. The CDB spectra show a marked difference between eutectic and hypoeutectic BG alloys; that is, the spectrum of the hypoeutectic BG alloy is closes to that of Zr metal than that of the eutectic BG alloy. This result exhibits that the elemental fraction of Zr atoms around free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. The CDB ratio profiles for the hypoeutectic BG alloy during annealing shows no appreciable change. The same trend was observed in the eutectic BG alloy.

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