Modification of Hypereutectic Al-17.5Si Alloy by Nd

摘要

In this paper, modification of hypereutectic Al-17.5%Si alloy by Nd was investigated. The modification mechanism was studied by OM, SEM and XRD. The results of OM and SEM analysis showed that pure Nd could effectively refine primary and eutectic silicon in hypereutectic Al-17.5%Si alloy. When Nd addition was 0.3%, the average grain size of primary silicon reached its minimum. The average grain size of primary silicon was reduced from 40～60μm to 10～30μm after modification. XRD patterns showed that no new phase formed after Nd modification. The results of mechanical properties test showed that whole properties of modified samples were significantly improved. When Nd addition was 0.3%, tensile strength of the alloy reached its maximum. Tensile strength was increased about 35.8% from 120MPa to 163MPa. Elongation was increased about 175% from 0.8% to 2.2%. The improvement of mechanical properties should attribute to fine primary and eutectic silicon after modification.