**4. Conclusions**

The dynamic mechanical properties of LaCe-based bulk metallic glasses were investigated by dynamic mechanical analysis. The experimental results reveal that the mechanical and thermal properties strongly depend on chemical composition. Substitution of Cu by Co enhances β relaxation due to the reduction of the enthalpy of mixing fluctuation. Physical aging below the glass transition temperature *T*g reduces the concentration of local "defects" in metallic glasses and causes a decrease of the intensity for the β process. The curves of loss modulus can be well fitted by the KWW model, the fitting parameter β*KWW* is approximately 0.4, indicating that the plastic deformation of the (La0.5Ce0.5)65Al10(Co0.8Cu0.2)25 metallic glass is related to the microstructural heterogeneity.

**Author Contributions:** M.L., Q.H. and Y.C. conducted the experiments and analyzed the experimental results. Q.H. and M.L. contributed to the sample preparation. M.L., J.Q., D.C., Y.Y. and J.-M.P. proposed the idea of the work, originated the experiment and write the paper.

**Funding:** This research was funded by the Fundamental Research Funds for the Central Universities (Nos. 3102018ZY010, 3102019ghxm007 and 3102017JC01003), Astronautics Supporting Technology Foundation of China (2019-HT-XG) and the Natural Science Foundation of Shaanxi Province (No. 2019JM-344). The investigation of Y.H. Chen and M.N. Liu sponsored by the Seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University (No. ZZ2019014). D. Crespo acknowledges financial support from MINECO, Spain, gran<sup>t</sup> FIS2017-82625-P, and Generalitat de Catalunya, gran<sup>t</sup> 2017SGR0042.

**Conflicts of Interest:** The authors declare no conflict of interest.
