Evolution process of T1 precipitate in Al–Cu–Li–TiC/TiB2 alloy during aging treatment

Abstract

In this study, particle-reinforced aluminium matrix composites (PRAMCs) of an Al–Cu–Li alloy were prepared using nano-sized TiB₂+TiC particles. The relationship between TiB₂+TiC nanoparticles and T₁ precipitates during the ageing process, as well as the influence of TiC + TiB₂ particles on the growth process of T₁ precipitates during the ageing process, were investigated. The grain sizes of the A0 and A1 samples were found to be 249.89 μm and 86.42 μm, respectively. The dislocation density is greater in the deformed A1 sample. The coefficient of thermal expansion (CTE) effect generated by TiC and TiB₂ particles stimulates the precipitation process of T₁ precipitates. The A1 alloy reached the peak ageing state in a shorter time and yielded a greater number of T₁ precipitates. The precipitation process of T₁ precipitate is: SSSS→T_1P→T₁. The transition from T_1P (face-centered cubic, FCC) to T₁ (hexagonal close packing, HCP) entails a modification in the order of packing. The recently formed T_1P precipitate is attached to the established T₁ precipitate and extends along the c-axis through the shared copper-rich layer that has formed on both sides of the mature T₁ precipitate. The mechanical properties of sample A1 are optimal at T = 22h, with a yield strength, tensile strength, and elongation of 520 MPa, 553 MPa, and 8.2%, respectively. In comparison to the A0 sample, the yield strength and tensile strength exhibited an increase of 5.05% and 5.13%, respectively.