Effect of Nd on Primary Silicon and Mechanical Properties of Hypereutectic Al-17.5%Si Alloy

Abstract

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