<p>With increasingly stringent application environments, there is a growing demand for designing and fabricating of promising structural materials. Conventional metallurgical methods typically struggle to produce positive mixing enthalpy alloys with uniform microstructures and consistent properties due to mutual immiscibility and uncontrollable segregation during solidification. To this end, we employ a bottom-up approach to fabricate Cu-50 vol% Fe₅₅Cr₂₅Mo₁₆B₂C₂ positive mixing enthalpy composites, utilizing ultrafast high-temperature sintering and instantaneous quenching. The method effectively prevents liquid segregation during the molten state and allows precise control over the size and distribution of the two phases. In addition, incorporated metallic glass particles as the hard phase additives, which can quickly form the localized multi-phase nanocrystals and establish a robust interlocking structure with pure copper during rapid sintering. Upon rapid quenching, the two phases solidify with a tight and conformal interface, while the elemental cross-diffusion and phase separation are mitigated. The mechanical tensile strength of the resulting composite is approximately 8 times greater than that of pure Cu. The wear resistance improves by 40-50 times, and the Vickers hardness increases by a factor of 10. The innovative sintering method provides a feasible pathway for developing and manufacturing of positive mixing enthalpy composite materials.</p>