High volume fraction Si particle-reinforced aluminium matrix composites fabricated by a filtration squeeze casting route

A new method called filtration squeeze casting (FSC) was presented to fabricate high volume fraction Si particle-reinforced aluminium matrix composites (Sip/Al) for electronic packaging applications. The Sip/Al composites exhibited a CTE of ~ 8.70 ppm/K, a TC above 119.80 W/(m·K) and a density of ~ 2.47 g/cm3 as well as a flexural strength above 163 MPa. Fracture of large Si particles occurred during FSC, resulting in a decreased size of Si particles and hence an increased mechanical property and a decreased TC. The average size of Si particles of ~ 29 μm is much smaller than that of the conventional hypereutectic Al–Si alloy but slightly larger than that of Sip/Al composites fabricated by spray deposition, resulting in balanced mechanical and physical properties. Dilution treatment decreased the amount of eutectic silicon in the matrix, leading to a considerable increase in TC and a negligible decrease in flexural strength and hardness. The flexural fracture mode is as follows. First, when the load borne by a silicon particle is beyond its fracture strength, it breaks. Then, the cracks caused by the fracture of Si particles propagate along interfaces between silicon particles and matrix Al. Finally, the link of these cracks result in the failure.