The effect of squeeze casting process on the microstructure, mechanical properties and wear properties of hypereutectic Al–Si–Cu–Mg alloy

Abstract

The effects of the squeeze casting process on the microstructure, mechanical properties and wear characteristics of hypereutectic Al–Si–Cu–Mg alloys have been investigated by optical, scanning and transmission electron microscopy and mechanical property test; the wear behaviour was investigated using a pin-on-disc configuration; alloy ingots were prepared by gravity casting, liquid squeeze casting and semisolid squeeze casting. The results show that the Si phase was refined and the α-Al dendrites transformed to rosette grains after semisolid squeeze casting. The peak intensity of the second phase decreased after extrusion, indicating that extrusion promotes the dissolution of solute elements into the matrix. Among the three casting processes, the alloys formed by semisolid squeeze casting had the best mechanical properties. Tensile strength, elongation and Brinell hardness reached 187.67 MPa, 2.33% and 142.5 HB, respectively. After semisolid squeeze casting, the morphology of the wear surface was flat and the number of spalling pits and furrows is less. Meanwhile, the friction coefficient and wear loss of the alloy sample are minima. Due to the uniform distribution of Si phases and equiaxed crystallization of α-Al phase in semisolid squeeze casting Al–Si–Cu–Mg alloys, the wear resistance is markedly enhanced.