Microstructure and mechanical properties of CeO2-coated graphene oxide reinforced 7075 composites subjected to equal channel angular pressing

The microstructure, mechanical performances and strengthening mechanisms of CeO 2 @GO/7075 composites processed by ECAP deformation treatment were studied. The findings displayed that ECAP deformation treatment obviously refined the grain microstructure of the composites, and the grain refinement effect decreased with increasing ECAP deformation temperature. Processed by 1 pass of ECAP deformation treatment at 250 °C, the mean grain size of the composites decreased from 42.0 μm to 10.9 μm. Additionally, a large number of dislocations, even dislocation tangles, were found in the composites after ECAP process. It was also found that these dislocations strongly interacted with nano-precipitates and interfaces, thus hindering the dislocation motion. Moreover, ECAP process could promote the further dispersion of the reinforcements, while the interfacial bonding between the Al matrix and the reinforcements was not damaged by the large shear force generated by ECAP process. As a result, the reinforcements could still play the role in the load transfer. Therefore, ECAP process could significantly improve the mechanical performances of CeO 2 @GO/7075 composites. Process by 1 pass of ECAP deformation treatment at 250 °C, the yield strength (504.8 MPa) and ultimate tensile strength (560.6 MPa) of the composites were obviously increased, which increased by 57.0% and 41.4%, respectively, compared to the composites before ECAP process. The improvement of the strength of CeO 2 @GO/7075 composites by the ECAP process was mainly due to the dislocation strengthening, which made up 42.3% of total strength contributions.