Combining effects of TiB2 and La on the aging behavior of A356 alloy

In the present work, the combining effects of TiB2 and La on the aging behavior of A356 alloy were investigated by comparing microstructures and age-hardening curves. The results demonstrated that, with the addition of TiB2, the density of precipitates upon aging is increased with a smaller size due to the increased dislocation density caused by the coefficient mismatch of thermal expansion between the matrix and reinforcements, therefore significantly increasing the aging hardness of the matrix. La helps to refine the SDAS of the α-Al grains and disperse the TiB2 particles and leads to an acceleration in the aging kinetics which shortens the peak-aged time by some 30 min based on the existence of TiB2, further improving the aging precipitation hardening. Further, it was also noted that the La alloyed composite achieved a superior tensile property due to the improved aging precipitation strengthening.