Measurement of the eutectic point of Fe–C alloy under 5 GPa

The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis (HPDTA) was utilized to measure the melting temperatures of Fe–C alloy (3.4–4.2 wt.% C) under 5 GPa and to plot the liquidus temperature curves spanning from hypoeutectic to hypereutectic compositions. Our results indicate that under 5 GPa, the carbon content at the eutectic point of the Fe–C alloy decreases to 3.6–3.7 wt.% C, representing a reduction of approximately 0.6 wt.% C compared to the atmospheric pressure value (4.3 wt.% C). Concurrently, the eutectic temperature rises to 1195 °C, showing an elevation of 48 °C relative to the atmospheric pressure condition (1147 °C). Microstructural analysis, x-ray diffraction (XRD), and hardness tests further corroborate these findings, demonstrating that high pressure significantly suppresses the solubility of carbon in γ-Fe, resulting in a decrease in the eutectic carbon content. Additionally, the hardness of the Fe–C alloy under 5 GPa is increased by more than 50% compared to that of the same type of Fe–C alloy under atmospheric pressure. This study provides essential experimental data for constructing high-pressure Fe–C phase diagrams and offers valuable insights for the design of high-performance Fe-based materials under extreme conditions.