Superior Strength and Ductility of In Situ Nano TiB₂/Al-Cu-Mg Composites by Cold Rolling and Post-Aging Treatment

In this work, the combination of cold rolling with post-aging treatment is developed to achieve the optimal strength-ductility for the in situ nano TiB₂/Al-Cu-Mg composite. The microstructure and mechanical properties of the composite subjected to 20% thickness reduction of cold rolling at room temperature and their evolutions upon post-aging at different temperatures were investigated by means of a tensile test, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the TiB₂ particles were effective in dislocation pinning and accumulation during the cold-rolling process. The tensile tests indicated that both the yield and ultimate tensile strengths of the cold-rolling sample increased a lot due to the dislocation strengthening and precipitation strengthening generated by dynamic precipitation during cold rolling in comparison with the conventional T6 sample. After aging at 100 °C/12 h, the elongation to failure reached ~8.4%, which was higher than the conventional T6 sample. Meanwhile, there was also a dramatic increase of strength. The yield and ultimate tensile strengths are ~644 MPa and ~726 MPa, respectively. This remarkable strength-ductility combination was due to the modified microstructure caused prior to artificial aging by the cold-rolling method and the formation of nanosized Guinier-Preston-Bagaryatsky (GPB) zones. The underlying mechanisms related to the superior strength-ductility combination were discussed regarding the microstructural characteristics in the composite.