Study on the Influence of Erbium and Preheating Process on Mechanical Properties of As-Cast 7055 Aluminum Alloy

Abstract

Although 7055 aluminum alloy is a deformed aluminum alloy and shows excellent mechanical properties after recrystallization and large deformation, through this method, its application range is enriched if rare earth is added, and the rare earth phase dispersion is promoted by heat treatment. This article used optical microscopy, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), micro Vickers hardness, and room temperature stretching methods to study the as-cast 7055-xEr (x = 0 wt.%, 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.%) aluminum alloy after being subjected to 460 °C × 3 h homogenization and 410 °C × 1 h solid solution + 150 °C × 12 h aging treatment for the changes in its microstructure and properties. The results indicated that: when 0.2 wt.%Er was added to 7055 aluminum alloy after a solution at 410 °C × 1 h and aging at 150 °C × 12 h, the dendrite structure was significantly reduced, the grain thinning was obvious, and the distribution was uniform; the Al8Cu4Er phase appeared in the lamellar eutectic η-Mg(Zn,Al,Cu)2 structure at grain boundaries, and the hardness reached 168.8 HV. The yield strength, tensile strength, and elongation were 542.12 MPa, 577.67 MPa, and 8.36%, respectively.