Effect of TiN-Coated Al Powders on the Microstructure and Mechanical Properties of A356 Alloy

The core/shell nano-TiN-coated Al powders (TiN/Al) were prepared and added into A356 alloy by ultrasonic-assisted casting method in this work. The results show that TiN/Al has a better dispersion in A356 matrix and a stronger strengthening effect than TiN without the core/shell structure. With the addition of TiN/Al, most of the coarse primary α-Al dendrites of A356 turn into equiaxial. After T6 heat treatment, it is found that eutectic silicon in A356 with TiN/Al becomes columnar or globular in shape and smaller in size, which causes a greatly enhanced elongation of 11.7%. The results also suggest that the addition of nanoparticles can affect the precipitation behaviors and change the shapes and sizes of the precipitation.