A Comparative Study on Microstructure, Mechanical Property and Damping Capacity of Hypoeutectic Al–Si–Cu Alloy for Different Casting Technologies

The paper comparatively investigates the microstructure, mechanical, and damping properties of hypoeutectic Al–Si–Cu casting alloys prepared by the cooling slope casting and thixoforming process. Microstructural analysis shows that cooling slope process refined the grains and promoted the transformation of equiaxed dendritic α-Al to rosette morphology. Subsequent thixoforming further enhanced this refinement, generating a microstructure of α-Al globules and spheroidized eutectic silicon particles. These microstructural alterations significantly improved their mechanical properties. Notably, the thixoformed samples exhibited a remarkable increase in yield strength from 139 to 193 MPa (38%), ultimate tensile strength from 145 to 205 MPa (42%), and fracture elongation from 1.1 to 3.2%. The damping analysis revealed a significant increase in both the loss modulus and damping capacity, while the storage modulus decreased at high temperatures for all samples. Consequently, the thixoformed samples displayed a distinct improvement in both their mechanical characteristics and damping capability.