Effect of Zr Addition on Microstructure and Properties of Al–Sn–Cu Based Alloy

Abstract

The microstructure of the Al–0.3Sn–0.3Cu alloy and Al–0.3Sn–0.3Cu–0.15Zr alloy has been examined by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), the mechanical properties have been evaluated by the tensile strength and microhardness tests. After addition of Zr, fine Al₃Zr precipitates provide a core for Sn during the solidification process; at the same time, Sn plays an important role in the distribution of θ(Al₂Cu) phase. These reasons lead to demixing of the β(Sn) phase and Al₂Cu phase obviously during the extrusion. Under the joint action of Al₃Zr and Sn, the Sn–θ(Al₂Cu) quasi-binary phase is distributed in the matrix uniformly. The Al₃Zr particles hinder the dislocation slip, make the intermediate subboundaries keep a stable state, and enhance the recrystallization resistance. Based on these reasons, the mechanical properties of the Al–0.3Sn–0.3Cu–0.15Zr alloy have been significantly improved.