The formation of atomic-level interfacial layer and its effect on thermal conductivity of W-coated diamond particles reinforced Al matrix composites

Diamond particles coated with a 45 nm-thick W layer were used to produce diamond particles reinforced Al matrix composites (Al/diamond(W)) by a gas pressure infiltration method. The results show that W atoms have diffused into Al matrix and replaced Al atoms during infiltration. As a result, a uniform 0.5 nm-thick Al5W interfacial layer is formed in the composite produced with 20 min infiltration time. The generation of the Al5W layer strengthens not only the interfacial bonding but also impedes the formation of hydrolysable Al4C3 phase. With increasing infiltration time from 10 to 60 min, the thermal conductivity increases from 520 to 620 W/m K, which manifests the influence of interfacial layer thickness on thermal properties of the Al/diamond(W) composite. The study provides a new strategy to modifying the interfacial structure of Al/diamond composites on the aspects of both enhancing the thermal conductivity and preventing the formation of hydrolysable Al4C3 phase.