Low-temperature densification and microstructure of W–Cu composites with Sn additives

Dense and homogeneous W–Cu composites with high strength were successfully prepared from Cu-coated W powders by hot pressure sintering (800 °C) with Sn as activated additives. The relative density, microstructure and properties of W–Cu composites with Sn additives were studied. The results have indicated that the addition of Sn additives could significantly promote the densification of W–Cu composites. When Sn was added as additives, the sintering process is mainly the sintering between Cu–Cu and Cu–Sn, and the better mobility of Cu–Sn solid solution is help to eliminate pores and promote low-temperature densification. The relative density of sintered composites has reached 99.2% with 2 wt.% Sn additives. Stacking faults and Twin structure can be distinctly observed in the Cu matrix when 2 wt.% Sn was added as additives. With adding of Sn additives，the Vickers hardness has increased to 263.5 HV. The addition of Sn can lead to the strengthening of interface bonding of sintered composites, and the fracture microstructure with the ductile fracture of Cu matrix and the trans-granular fracture of W phase has been observed in the sintered composites with Sn additives. The bending strength of sintered composites has increased to 993.1 MPa due to the transform of fracture mechanism of sintered composites. The coefficient of thermal expansion of sintered composites has reduced to the minimum value of 7.56 × 10−6/K with the 1.5 wt.% Sn additives.