Effect of graphite flakes particle sizes on the microstructure and properties of graphite flakes/copper composites

Copper matrix composites were successfully prepared from the mixtures composed of modified copper-coated graphite flakes and copper powder via vacuum hot pressing process. Under the condition with same volume fraction of graphite flakes, the particle size of graphite flakes had a great effect on the properties of graphite flakes/copper composites. The phase compositions and microstructure of the composites were analyzed by XRD and SEM, respectively. Thermophysical and mechanical properties performance of composite materials were analyzed with different particle sizes of graphite flakes. The results showed that with the increasing of particle size, the thermal conductivity of composites in X-Y direction (basal plane of graphite flake) increased and coefficient of thermal expansion of composites in X-Y direction initially decreased and then increased. As the particle size of graphite flakes decreased, the bending and compressive strength increased. When the equivalent particle size of graphite flakes was 292 μm, the composites had superior thermal conductivity (612 W m−1 k−1), ideal flexural strength (42.5 MPa), suitable electrical conductivity (14.7% international annealed copper standard) and apposite coefficient of thermal expansion (6.6 ppm k−1). [Display omitted] •The equivalent particle size model was introduced to analyze the composite.•The predicting model for the TC of GFs/Cu composite was established.•The fracture mechanism of composite in two directions was preliminarily explored.