Effect of cold rolling deformation on microstructure and properties of Al₂O₃/Cu composites

In order to further enhance the room temperature mechanical properties of Al₂O₃ composites, 0.57wt%Al₂O₃/Cu composites were prepared by internal oxidation method. The effects of different cold-rolling deformation on the microstructure, electrical conductivity, and mechanical properties of Al₂O₃/Cu composites were studied, focusing on the contribution of various strengthening mechanisms to the strength of composite under different amounts of deformation. The results show that the grains of Al₂O₃/Cu composites gradually change to elongated fiber-like structure with increasing cold rolling deformation, and the average grain size decreases from 2.82 μm (initial state) to 0.56 μm (90% deformation). The mechanical properties of the composites gradually improve with increasing cold rolling deformation, peaking at 60% deformation, with a strength of 544 MPa and a hardness of HV 156, which are increased by 35% and 14%, respectively, while the electrical conductivity only decreases from 85%IACS to 83%IACS. This is due to the interaction between nanoscale Al₂O₃ particles and dislocations during cold deformation, grain boundary strengthening and dislocation strengthening gradually increase, and the calculated contributions values of grain boundary strengthening and dislocation strengthening increase from 160 MPa and 47 MPa to 264 MPa and 141 MPa, respectively. When the deformation exceeds 60%, the grain size (0.56 μm) and dislocation density (3.5×10¹⁴ m⁻²) tend to stabilize, the contribution of dislocation strengthening and grain boundary strengthening reaches its peak, and the mechanical properties are optimal.