Effect of Sr–Ce modification on the microstructure and mechanical properties of A356 alloy

The effects of Sr–Ce addition on the structure and properties of A356 aluminum alloy are investigated under a constant of Sr content with increasing addition of Ce. When Sr is added to the aluminum melt in combination with Ce, the average secondary dendrite arm spacing reduces in the original matrix phase and decreases initially and later increases with the increase of Ce concentration. In addition, the iron-rich phase changes from coarse acicular structure to Chinese script and short rod-shaped structures, and Ce adsorb on the surface of the iron-rich phase resulting in the transformation of β-Al5FeSi into π-Al8Mg3FeSi6. When Ce content is 0.06%, the best modification effect is achieved. The tensile strength and elongation of the as-cast alloy reach 202MPa and 11.4%, which are 1.5% and 65.2% higher than those of adding Sr alone; the values after T6 heat treatment are 276 MPa and 13.3%, which are 12.7% and 22.0% higher than those of adding Sr alone, respectively.