Effect of Al–P–Ti–TiC–Nd2O3 modifier on the microstructure and mechanical properties of hypereutectic Al–20 wt.%Si alloy

The effect of Al–P–Ti–TiC–Nd2O3 modifier on the microstructure and mechanical properties of hypereutectic Al–20 wt.%Si alloy has been investigated. It has been concluded that Nd2O3 in Al–P–Ti–TiC–Nd2O3 modifier can modify primary silicon in hypereutectic Al–Si alloys. Statistical analysis shows that primary silicon size (approximately average 38 μm) in modified Al–20 wt.%Si alloy with Al–P–Ti–TiC modifier is larger than that (approximately average 20 μm) in modified Al–20 wt.%Si alloy with Al–P–Ti–TiC–Nd2O3 modifier. Compared with primary silicon modified with Al–P–Ti–TiC modifier, Primary silicon modified with Al–P–Ti–TiC–Nd2O3 modifier has the smaller size at different holding times such as 10, 60 and 120 min. The internal defects in coarser primary silicon particles play an important role in determining the tensile strength and elongation of the materials. Coarser primary silicon particles in unmodified Al–Si alloys can degrade the loading bearing capacity of the materials. Modification can eliminate the internal defects to a great extent and improve the tensile strength and elongation of hypereutectic Al–Si alloys. Compared with unmodified and heat-treated Al–20 wt.%Si alloy, the tensile strength of the modified with Al–P–Ti–TiC–Nd2O3 modifier and heat-treated Al–20 wt.%Si alloy increases by 20%.