Properties of $\mathrm{Ce}$-based bulk metallic glass-forming alloys

We find that a family of $\mathrm{CeAlNiCu}$ alloy system can be readily cast into bulk glassy rods with up to $3\mathrm{mm}$ diameter. The $\mathrm{Ce}$-based bulk metallic glasses (BMG’s) exhibit a wide supercooled region up to $78\mathrm{K}$, very low glass transition temperature $\left(T_g=359\mathrm{K}\right)$, and Debye temperature $\left({\theta }_D=144\mathrm{K}\right)$. The glass formation, crystallization, glass transition, liquid behavior, and elastic and acoustic properties of the $\mathrm{CeAlNiCu}$ alloys are investigated. Ultrasonic measurements demonstrate that the $\mathrm{Ce}$-based BMG’s are the softest in elastic moduli in known BMG’s due to their very low glass transition temperature. The fragility parameter $\left(m\right)$ is determined to be 21, indicating the strong liquid behavior of the alloy concerning the temperature dependence of viscosity. A remarkable large softening of long-wavelength acoustic phonons in the BMG relative to its crystalline state is observed, and the phonon softening is attributed to its intrinsic microstructural features and strong liquid behavior.

Figure 1

(a) XRD patterns of the as-cast ${\mathrm{Ce}}_{60}{\mathrm{Al}}_{10}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{20}$ alloy. (b) DSC trace of crystallization and glass transition processes. (c) Melting process of the ${\mathrm{Ce}}_{60}{\mathrm{Al}}_{10}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{20}$ alloy.

Figure 2

DSC traces of the $\mathrm{Ce}$-based BMG’s with different compositions and critical diameters.

Figure 3

DSC traces of ${\mathrm{Ce}}_{60}{\mathrm{Al}}_{10}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{20}$ BMG at different heating rates from 2 to $20\mathrm{K}∕\min$. The inset shows the Kissenger plot of the $T_x$.

Figure 4

The dependence of $T_g$, $T_x$, and $\Delta T_x$ of the ${\mathrm{Ce}}_{60}{\mathrm{Al}}_{10}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{20}$ BMG on the heating rate $\varphi$.

Figure 5

The rough linear relation between $E_a$ and $T_x$ of the $\mathrm{Ce}\text{−}$, $\mathrm{Zr}\text{−}$, $\mathrm{Pd}\text{−}$, $\mathrm{Fe}\text{−}$ $\mathrm{Cu}\text{−}$, $\mathrm{Co}\text{−}$, and $\mathrm{Pr}$-based BMG’s.

Figure 6

The Lasocka’s relationship of $T_g$, $T_x$, and $\varphi$ of the ${\mathrm{Ce}}_{60}{\mathrm{Al}}_{10}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{20}$ BMG in the heating rate range of 2 to $200\mathrm{K}∕\min$.

Figure 7

VFT relationship between $T_g$ and $\varphi$.