Influence mechanisms of Zr and Fe particle additions on the microstructure and mechanical behavior of squeeze-cast 7075Al hybrid composites

The different influence of Zr and Fe particle additions on the microstructure and mechanical behavior of 7075Al matrix composites reinforced with 40 vol% SiCp has been systematically investigated. The results indicate that Zr particles are well retained and the interfaces between the Al matrix and Zr particles are clean following the preparing process. However, a hard and brittle Fe-Al layer with an average thickness of 12 mu m is generated at the interfaces between the Al matrix and Fe particles. As a result, the as-cast AMC-Zr composite exhibits the best ultimate tensile strength, fracture strain and Young's modulus with values of 564 MPa, 1.12% and 151.3 GPa, respectively. On the contrary, the addition of Fe particles degrades the mechanical properties of the SiCp/7075Al composite. The difference in the mechanical properties results from interface structure and micro-zones surrounding metallic particles. The micro-zones formed by Zr particle additions have good damage tolerance and hinder the crack propagation in the AMC-Zr composite. However, the formation of hard and brittle Fe-Al interfacial layers result in the random development of the crack propagations in the AMC-Fe composite. In terms of fracture mechanics, the AMC-Zr composite shows a feature of mixed ductile and brittle fracture, and the Zr particles are rarely found in the fracture because of good interface bonding. However, most Fe particles in the fractured AMC-Fe composite exhibit interfacial debonding with the Al matrix. (C) 2019 Elsevier B.V. All rights reserved.