Ce-based Metallic Glasses Research Articles

Three-point bending fracture characteristics of bulk metallic glasses

This paper presents the SEM micrographs for the three-point bending fracture surfaces of Zr-based, Ce-based and Mg-based bulk metallic glasses (BMGs), which show the dimple structures in the three kinds of BMGs. The shapes of the giant plastic deformation domain on the fracture surface are similar but the sizes are different. The fracture toughness K C and the dimple structure size of the Zr-based BMG are both the largest, and those of the Mg-based BMG are the smallest. The fracture toughness K C and the dimple structure size of the Ce-based BMG are between those of the Zr-based and the Mg-based BMG. Through analyzing the data of different fracture toughnesses of the BMGs, we find that the plastic zone width follows w = (K C/σ Y)2/(6π).

Anomalous temperature dependent elastic moduli of Ce-based bulk metallic glass at low temperatures

We report the abnormal temperature dependent elastic moduli of Ce-based bulk metallic glass (BMG) at low temperatures. Unlike other BMGs with stiffness mode, the Ce-based metallic glass exhibits an anomalous softening longitudinal acoustic mode with the decrease of temperature. Particularly, the bulk modulus shows a continuous decrease upon cooling indicating the softening of the BMG, which is completely different from that of other metallic glasses and conventional alloys. The physical origin of this abnormal elastic behavior is attributed to the alterative valences and electronic configurations at low temperatures.

Shear modulus as a dominant parameter in glass transitions: Ultrasonic measurement of the temperature dependence of elastic properties of glasses

Temperature dependence of elastic properties of a Ce-based metallic glass and a polymeric glass covering glass transition is in situ studied using an ultrasonic method. We find that the transverse acoustic velocity drops sharply consistently at the calorimetric glass transition temperature ${T}_{g}$, while the longitudinal velocity shows sudden decrease substantially above calorimetric ${T}_{g}$. Only the breakdown of the shear modulus $G$ was detected, in contrast to the weak $T$ dependence of bulk modulus around ${T}_{g}$. The results demonstrate that the $G$ can precisely control the liquid behaviors of glass forming liquids and support the models of the shear interaction and/or energy dominated glass transition.

Compressive deformation of a bulk Ce-based metallic glass

We numerically investigate the transport behavior of a quasi-one-dimensional (1D) square loop device containing the Rashba spin-orbital interaction in the presence of a magnetic flux. The conductance versus the magnetic field shows the Al'tshuler-Aronov-Spivak (AAS) and Aharonov-Bohm (AB) oscillations. We focus on the oscillatory amplitudes, and find that both of them are strongly dependent on the spin precession angle (i.e., the strength of the spin-orbit interaction) and exhibit no periodic oscillations, in good agreement with a recent experiment by Koga [cond-mat/0504743 (unpublished)]. However, our numerical results for the ideal 1D square loop device for the node positions of the amplitudes of the AB and AAS oscillations are found to show some discrepancies with the results for quasi-1D square loops with a finite width. In the presence of disorder and taking the disorder ensemble average, the AB oscillation in the conductance disappears, while the time-reversal symmetric AAS oscillation still remains. Furthermore, the node positions of the AAS oscillatory amplitude remain the same.

Indentation Creep Behavior in Ce-Based Bulk Metallic Glasses at Room Temperature

The room temperature creep behaviors of Ce-based bulk metallic glasses were examined by the use of nanoindentation. The creep rate and creep rate sensitivity of Ce-based BMGs were derived from indentation creep curves. The low creep rate sensitivity of Ce-based BMGs indicates that the room temperature creep is dominated by localized shear flow. The experimental creep curves can be described by a generalized Kelvin model. Furthermore, the creep retardation spectrum is calculated for the Ce-based metallic glasses. The results showed that creep retardation spectrum consists of two relatively separated peaks with the well defined characteristic relaxation times.