*3.3. Analysis of DSC*

Figure 4 shows the DSC thermograms of amorphous alloys of both Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %). From the figure, it can be found that there is an obvious and broad glass transition region. Due to the large atomic size difference and negative mixing heat among the multi-components of the bulk amorphous alloy, the nucleation and growth rate of the crystalline phase of the alloy are inhibited. As a result, a stable supercooled liquid phase region appears in the alloy before crystallization. It can be seen from the figure that there are differences in the supercooled liquid phase (ΔTx) of the two alloys before crystallization, which are about 80 K and 90 K, respectively, and this is not common in the Ti-based amorphous alloy system. The single exothermic peak is generated by the interaction of several crystal phases. The crystalline mode implies that the atomic rearrangements of the constituent elements on a long-range scale are necessary for the progress of the crystallization reaction. This inevitably leads to a delay in the crystallization reaction, resulting in a high thermal stability of the supercooled liquid. In such supercooled liquids, the topological and chemical short-range order will be greatly enhanced, and the structure will also change, which is conducive to the formation of high-density random packing structures, which are typically characterized by low atomic diffusivity. In general, the higher the stacking density of atoms, the better the thermal stability of the amorphous alloy and the greater the resistance of the supercooled liquid to the crystal transformation that is, the higher the glass-forming ability of the amorphous alloy [31]. All these further improve that both Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %) alloy ribbons with a large, supercooled liquid region possesses a high glass-forming ability and can be consolidated into a bulk form by taking advantage of the large viscous flow in the supercooled liquid region.

**Figure 4.** DSC thermograms of amorphous alloys of both Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %).

#### *3.4. The Potentiodynamic Polarization Curve*

In order to gain a deeper and more comprehensive understanding of the corrosion behavior of these two amorphous alloys, electrochemical measurement was performed in 3 mass% NaCl solution. Before the start of the corrosion test, the alloy specimens were mechanically polished in cyclohexane with silicon carbide paper up to grit 2000, degreased in acetone, washed in distilled water, dried in air and further exposed to air for 24 h for good reproducibility. Figure 5 shows the potentiodynamic polarization curve of both Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %) amorphous alloys in 3 mass% NaCl solution open to air at 298 K. As seen in Figure 5, pure Ti and Ti6Al4V alloys are passivated with different current densities. However, both amorphous alloys kept steady current densities at about 0 A.m−2, which suggests that both were hardly eroded by the 3 mass% NaCl solution. Based on the data, it is concluded that the both amorphous alloys relatively possess excellent corrosion resistance compared with pure Ti and Ti6Al4V alloys in the Cl- -containing solutions or brine. Ti and Zr are known as strong passive valve metals in aggressive environments, and the enrichment of Ti and Zr in the surface film was found in Ti- and Zr-containing Ni-based glassy alloys [31]. This indicates that the improved corrosion resistance of the two amorphous alloys is mainly due to the formation of a protective film rich in Ti and Zr on the surface of the alloys in the NaCl solution. In addition, the improvement of corrosion resistance is also related to the structural and chemical uniformity of amorphous alloys.

**Figure 5.** The potentiodynamic polarization curve of both Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %) amorphous alloys in 3 mass% NaCl solution open to air at 298 K.

#### **4. Conclusions**


In this study, in order to ensure the accuracy of the two alloy compositions and the reliability of the results, it is suggested to test the composition of the two alloys before the experiment. Titanium-based alloys are widely used in biomedical fields because of their excellent biocompatibility and biological activity. Especially as a biological implant material, it plays an important role. The elastic modulus, excellent biocompatibility and excellent corrosion resistance make it develop rapidly. The results of this study about Ti75Zr11Si9Fe5 (At %) and Ti66Zr11Si15Fe5Mo3 (At %) will be beneficial to promote the development and application of titanium alloy implant materials.

**Author Contributions:** Conceptualization, L.B.; Experiment, L.B. and C.C.; Methodology, H.Z.; Resources and Data Curation, H.Z. and Z.D.; Writing—Original Draft Preparation, L.B. and Writing— Review and Editing, L.B. and Z.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Program of 2021 Henan Province Key R&D and Promotion Project (Science and Technology) (212102210551).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this work are available on request from the corresponding authors.

**Acknowledgments:** Many thanks to the support of the research group members.

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

#### **References**

