Microstructure evolution and aging strengthening behavior of in-situ TiC nano-reinforced Al-Si-Cu-Mg alloy

Abstract

The effect of in-situ synthesized TiC nanoparticles on the microstructure evolution and aging behavior of Al-Si-Cu-Mg alloy for engineering structural applications was systematically studied. The composites were analyzed using high resolution transmission electron microscopy) HRTEM, small angle neutron scattering (SANS), and first-principles calculations. The results showed that the TiC nanoparticles are fully coherent with the aluminum matrix, effectively reducing the supercooling required for α-Al nucleation and decreasing the secondary dendrite arm spacing. In addition, the introduction of nanoparticles shortened the peak aging time. The peak yield strengths of the alloy before and after the introduction of nanoparticles were 245 MPa and 270 MPa, respectively. SANS calculations revealed a rapid increase in the volume fraction of precipitates after 4 h of aging, with stabilization occurring at 16 h. Under peak aging conditions, the TiC-reinforced alloy exhibited a higher volume fraction of θ´ precipitates and smaller precipitate sizes. This is due to the increased strain at the Al/TiC interface, which induces greater lattice distortions and promotes the generation of dislocations. These dislocations accelerate solute atom migration, enhancing the precipitation process. Furthermore, both TiC nanoparticles and the metastable θ´ phase act as strong pinning sites for dislocations, contributing to the alloy's improved strength.