Effect of nano-TiC/TiB2 particles on the recrystallization and precipitation behavior of AA2055-TiC+TiB2 alloys

Abstract

In this study, particle-reinforced aluminum matrix composites (PRAMCs) of 2055 Al–Cu–Li alloy were prepared with nano-sized TiB2+TiC particles, and electron probe microanalyzer (EPMA), differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to investigate the recrystallization and aging behavior of 2055 + TiB2+TiC alloy. The relationship between TiB2+TiC nanoparticles and the T1 strengthening phase during aging was investigated, and the promotion effect of nanoparticles on the T1 phase during aging was explained by the stored energy and mismatch in the coefficient of thermal expansion (CTE). The grain size of as-cast 2055, 0.5, and 1.0 alloys were 112 μm, 87 μm, and 68 μm, respectively. The TiB2+TiC nanoparticles were found to hinder the development of α-Al dendrites in solidification and refine the grains. The recrystallization behavior during solid solution treatment was mainly a particle stimulated nucleation (PSN) mechanism, and TiB2+TiC nanoparticles enhanced the recrystallization resistance. The number density of T1 phase in the pre-deformed 2055 + TiB2+TiC alloy was 452 ± 12/μm−2 with an average size of 73 ± 3 nm, which was finer than 2055 alloy, resulting from the retention of more dislocations or CTE effects at the TiB2 or TiC interface in the deformed 0.5 or 1.0 alloy. These factors cause Cu atoms to aggregate and provide favorable conditions for T1 phase precipitation. Compared with 2055, the ultimate tensile strength of the 0.5 sample was increased from 424 MPa to 455 MPa under condition A and from 498 MPa to 550 MPa after pre-deformation. This study can be used as a reference for improving the mechanical properties of Al–Li alloys.