# Phase Equilibria of Si-C-Cu System at 700 °C and 810 °C and Implications for Composite Processing

## TL;DR

This paper studies the phase behavior of silicon, carbon, and copper at two temperatures to improve the processing of composite materials.

## Contribution

The first experimental investigation of the Si-C-Cu system's phase equilibria at 700 °C and 810 °C, with implications for composite processing.

## Key findings

- At 700 °C, eight single-phase and six three-phase regions were identified.
- At 810 °C, higher solubility of C and Si/Cu was observed, with new phases like bcc and liquid.
- Optimal processing conditions produced composites with high bending strength of 998.61 MPa.

## Abstract

The phase equilibria of the Si-C-Cu ternary system at 700 °C and 810 °C were experimentally investigated for the first time. Fifteen key alloys were prepared via powder metallurgy and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Isothermal sections were constructed based on the identified equilibrium phases. At 700 °C, eight single-phase regions and six three-phase regions—(C)+(Cu)+hcp, (C)+hcp+γ-Cu33Si7, (C)+γ-Cu33Si7+SiC, γ-Cu33Si7+SiC+ε-Cu15Si4, SiC+ε-Cu15Si4+η-Cu3Si(ht), and SiC+(Si)+η-Cu3Si(ht)—were determined. At 810 °C, nine single-phase regions and seven three-phase regions were identified. The solubility of C and Si/Cu in the various phases was quantified and found to be significantly higher at 810 °C compared to 700 °C. Key differences include the presence of the bcc (β) and liquid phases at 810 °C. The results demonstrate that higher temperatures promote increased mutual solubility and reaction tendencies among Cu, C, and Si. Motivated by these findings, the influence of vacuum hot pressing parameters on SiC-fiber-reinforced Cu composites (SiCf/Cu) was investigated. The optimal processing condition (1050 °C, 60 MPa, 90 min) yielded a high bending strength of 998.61 MPa, attributed to enhanced diffusion and interfacial bonding facilitated by the high-temperature phase equilibria. This work provides essential fundamental data for understanding interactions and guiding processing in SiC-reinforced Cu composites.