**4. Conclusions**

Ti3SiC2/Cu composites were sintered by Spark Plasma Sintering (SPS) in a vacuum under a pressure of 35 MPa at 950–1050 ◦C. The as-synthesized composites were systematically characterized by scanning electron micrography (SEM), optical micrography (OM) and X-ray diffractometry (XRD), respectively. The results indicated that the constituent of the Ti3SiC2/Cu composites included Ti3SiC2, Cu3Si and TiC, which was insensitive to the sintering temperature. The reaction between Ti3SiC<sup>2</sup> and Cu produced Cu3Si and TiC, the formation of which was attributed to the presence of Cu and the de-intercalation of Si atoms Ti3SiC2. OM analysis confirmed that with the increase in the sintering temperature, the Ti3SiC<sup>2</sup> became smaller and smaller, which resulted from the more violent reaction between Ti3SiC<sup>2</sup> and Cu. Moreover, SEM analysis demonstrated that the agglomeration of Cu in the composites limited the uniformity of the microstructure distribution of the composites, governing the mechanical behaviors of the composites. At 1000 ◦C, the distribution of Cu in the composites was relatively uniform; thus, the composites exhibited the highest density, relatively high hardness and compressive strength. The relationships of the temperature, the current and the axial dimension with the time during the sintering process were further discussed, and a corresponding schematic illustration was proposed to explain the related sintering behaviors of the composites sintered by SPS.

**Author Contributions:** Conceptualization, R.Z.; Data curation, B.C. and H.Z.; Formal analysis, R.Z., B.C., M.S. and C.W.; Investigation, R.Z., F.L., M.S. and C.W.; Methodology, R.Z. and B.C.; Writing original draft, R.Z., B.C. and F.L.; Writing—review and editing, R.Z. and F.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Open Project of State Key Laboratory of Solid Lubrication, Chinese Academy of Sciences (LSL-2115), and Sichuan Province Key Research and Development Program (22SYX0017).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

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