Investigation on recrystallization and precipitation behaviors of Al-4.5Cu-1.5 Mg alloy refined by Ti-supported TiC nanoparticles

The recrystallization and precipitation behaviors of an Al-4.5Cu-1.5 Mg alloy refined by Ti-supported TiC nanoparticles (NPs) (TiC/Ti refiner) were investigated in detail, and the strengthening mechanism was discussed. The results indicated that the addition of TiC/Ti refiner promoted recrystallization of the Al-Cu-Mg alloy and decreased the average grain size to 76 μm. In the aging process, a portion of the dispersed TiC NPs acted as the substrate for S′ to precipitate from the matrix along Al <100> direction, because of the satisfactory matching relationship between the S′ (021)//Al (001)//TiC (001) planes. At the same time, the addition of TiC NPs decreased the precipitate-free zones and refined the grain boundary precipitates in the alloy. The NPs also promoted the precipitation of GPB zones and S′ phases, which reduced the cracking tendency, inhibited the dislocation motion and increased the comprehensive performance of the alloy. As a result, the yield strength, tensile strength and elongation of the TiC/Ti-refined Al-4.5Cu-1.5 Mg alloy reached 287 MPa, 421 MPa and 25.5%, indicating an increase of 22.6%, 14.7% and 109.1%, respectively, compared to the unrefined alloy.