Microstructure and Mechanical Properties at Elevated Temperature of Powder Metallurgy Al-Zn-Mg-Cu Alloy Subjected to Hot Extrusion

Abstract

In this work, Al-Zn-Mg-Cu powders containing 0.15 and 0.33 wt % oxygen were utilized to prepare high-strength aluminum alloys through the process of cold isostatic pressing, sintering, hot extrusion, and heat treatment. Microstructural and mechanical properties at elevated temperatures of 250, 350, and 450 °C were investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and high-temperature tensile tests. Results showed that the tensile strengths of the obtained Al-Zn-Mg-Cu alloys with 0.15 wt % oxygen were 185, 46, and 18 MPa at 250, 350, and 450 °C, respectively. When the oxygen content of Al-Zn-Mg-Cu alloy rose to 0.33 wt %, the tensile strengths at the corresponding temperature reached up to 205, 68, and 25 MPa, respectively. The excellent high-temperature performance could be attributed to double hindrance to dislocation motion and grain boundary migration by a large amount of nano γ-Al2O3 created by the in-creased oxygen, thereby resulting in fine grains even at high temperatures.

Effect of Hot Deformation and Heat Treatment on the Microstructure and Properties of Spray-Formed Al-Zn-Mg-Cu Alloys

“…Zhai et al [153] discovered that the formation of high-melting point Al 10 Cu 7 Sm 2 phases in Al-Zn-Mg-Cu-Zr alloys with Sm addition anchored grain boundaries during high-temperature deformation, thereby improving the high-temperature performance. Furthermore, the high-temperature performance of Al-Zn-Mg-Cu alloys, similar in composition to the 7055 alloy but without Zr, was studied by Han et al [154]. Their results indicated that increasing the oxygen content during the alloy preparation process allowed the formation of γ-Al 2 O 3 , which hindered dislocation movement and grain boundary migration, thus enhancing the high-temperature performance.…”

High-Temperature Mechanical Behavior of an As-Extruded Al-5Zn-2Mg-0.3Cu (in wt.%) Alloy

“…Since aluminum (Al) alloys have many advantages, such as low density, good strong plasticity, corrosion resistance, and good electrical and thermal conductivity, they have a wide application prospect in the fields of rail transit, ship, and aerospace [1][2][3][4][5]. At room temperature, their mechanical properties can well meet the standard of material selection for light-weight and high-strength structural materials [6].…”