Influences of Cu content on the microstructure and reinforcing behavior of network AlN/Al composites at 350 °C

Reinforcement configuration of Al composites has recently been at the center of attention. In this study, through the analysis of microstructure and tensile properties, effects of Cu content on the reinforcing behaviors of AlN network were investigated in details. Results indicated that the increasing amount of Cu would form micron Al2Cu which would decorated on the AlN network. With the increasing amount of Cu addition from 1.5% to 6%, the particle size of Al2Cu increased from 1 μm to 10 μm. Besides the micron Al2Cu, Cu elements were also existed in θ′ precipitates in the region where were poor of AlN and segregated on the surface of AlN. Given the microstructure changes with different Cu addition, the tensile properties at room temperature increased with Cu addition while the average tensile strength at 350 °C were decreased from 102 MPa to 85 MPa. The addition of elements would affect the bearing capacity of the 8.2AlN/Al–Cu composites at 350 °C. Firstly, the micron Al2Cu phase would suffer the load and get stress concentration. It would lead to the premature imitation of voids and strongly impair the strengthening behavior of AlN network. Secondly, the nano θ′ precipitates would become coarsen and the hinder effects of dislocation would be enhanced at 350 °C. Finally, the segregated Cu atoms on the AlN surface could increase the deformation coordination of AlN network and help decrease the stress concentration.