Microstructure and properties of copper matrix composites with diatomaceous earth fabricated by pulse plasma sintering

Novel copper–diatomaceous earth (DE) composites containing 5–20 vol.% DE were fabricated by plasma pulse sintering (PPS). Scanning electron microscopy revealed a homogeneous dispersion of DE particles and good interfacial bonding with the copper matrix. Increasing DE content effectively suppressed grain growth in copper, reducing the average grain size from 5.28 μm in pure Cu to 3.68 μm in the composite with 20 vol.% DE. The incorporation of DE led to a pronounced improvement in mechanical performance. Vickers hardness increased from 60.6 HV for pure Cu to 103.4 HV for the 20 vol.% DE composite, representing an enhancement of approximately 70%. Tensile tests showed a significant increase in yield strength, while the ultimate tensile strength remained comparable to that of sintered copper. Owing to the lower density of DE and the composite density following the rule of mixtures, these improvements translate into a substantial increase in specific mechanical properties. Thermophysical properties were also affected by DE addition. The coefficient of thermal expansion decreased slightly with increasing DE content, while thermal conductivity was markedly reduced from 390 to 222 W × m -1 × K -1 , approaching values typical of aluminum. These results demonstrate that diatomaceous earth is a promising, low-cost reinforcement for copper matrix composites, offering reduced weight and tailored mechanical and thermal properties.