Research Article

Nanomechanical properties and thermal decomposition of Cu-Al₂O₃ composites for FGM applications

National Technical University of Athens, School of Chemical Engineering, 9 Heroon Polytechneiou st., Zografos, Athens 157 80, Greece

^* e-mail: charitidis@chemeng.ntua.gr

Received: 27 July 2016
Accepted: 10 November 2016

Abstract

It is widely reported that copper-alumina (Cu-Al₂O₃) nanocomposite materials exhibit high potential for use in structural applications in which enhanced mechanical characteristics are required. The investigation of Cu-Al₂O₃ nanocomposites which are to form a functionally graded material (FGM) structure in terms of nanomechanical/structural integrity and thermal stability is still scarce. In this work, fully characterized nanosized Al₂O₃ powder has been incorporated in Cu matrix in various compositions (2, 5 and 10 wt.% of Al₂O₃ content). The produced composites were evaluated in terms of their morphology, structural analysis, thermal behavior, nanomechanical properties and their extent of viscoplasticity. The results reveal that all nanocomposites degrade at elevated temperatures; increased surface mass gain with decreasing Al₂O₃ content was observed, while no such difference of % mass gain in 5 and 10 wt.% of Al and Al₂O₃ content in Cu was observed. The increase of Al₂O₃ wt.% content results in thermal stability enhancement of the nanocomposites. The thermal decomposition process of the material is reduced in the presence of 10 wt.% of Al₂O₃ content. This result for the matrix decomposition can be explained by a decrease in the diffusion of oxygen and volatile degradation products throughout the composite material due to the incorporation of Al and Al₂O₃. The Al₂O₃ powder enhances the overall thermal stability of the system. All samples exhibited significant pile-up of the materials after nanoindentation testing. Increasing the wt.% of Al₂O₃ content was found to increase the creep deformation of the samples as well as the hardness and elastic modulus values.