Role of sintering atmosphere in controlling porosity, microstructure and performance of 3D printed polylactic acid/copper composites

Polymer/metal composites fabricated through Fused Filament Fabrication (FFF) represent a rapidly advancing domain with significant potential for functional applications. In this study, polylactic acid (PLA)/copper composite filaments were processed via FFF and subsequently subjected to identical debinding and sintering schedules under two distinct shrouding atmospheres, argon and aluminum-supported reducing carbon. The choice of sintering atmosphere was found to exert a decisive influence on densification, porosity evolution, shrinkage, and phase development. The results revealed that samples sintered under an argon-shrouded atmosphere exhibited superior densification (7.84 g/cm³), reduced porosity (~ 12.5%), improved particle bonding, minimized oxidation, and significantly enhanced thermal conductivity (13.02 W/m K) and diffusivity. In contrast, samples sintered under an aluminum-supported reducing carbon-shrouded atmosphere attained a lower density (6.95 g/cm³) and higher porosity (~ 22.4%), with the formation of secondary phases such as CuO, Al₄C₃, and α-Al₂O₃. The phases contributed to increased hardness (~ 38.86 HV) but resulted in a lower elastic modulus and non-uniform sintering. An alumina-supported reducing carbon atmosphere promotes controlled porosity and limits dimensional shrinkage, making it suitable for filtration and wick applications, whereas an inert atmosphere, such as argon, enhances thermal conductivity and mechanical stiffness, favoring high-performance structural applications. Overall, the selection of the sintering atmosphere was found to be pivotal in tailoring the final properties of the component. The results provide a framework for tailoring additive manufacturing strategies to improve the reliability and application potential of copper-based components in advanced thermal management systems.