Effect of different homogenization times on the mechanical properties of 7075 aluminum alloy

Abstract

The effects of homogenization temperature at 465 °C and different homogenization times (6h/12h/24h/36/h/48h) on the microstructure and mechanical properties of as-cast 7075 aluminum alloy were studied using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), hardness testing, and tensile testing. The results show that during the initial stage of homogenization, the continuous bright white network of σ-Mg (Zn, Cu, Al)2 phase transforms into a white broken flocculent S–Al2CuMg phase with the dissolution of Zn. In the middle stage, the S–Al2CuMg phase dissolves and Cu diffuses into primary Al7Cu2Fe, accompanied by precipitation of a large amount of dispersed nanoscale MgZn2 phase. With the homogenization time, the Al7Cu2Fe and MgZn2 phase are coarsened. The strength and plasticity of the alloy show a trend of first increase and then decrease. When the homogenization time is 24 h, the ultimate tensile strength (UTS), yield strength (YS), and elongation reach the peak values of 231.1 MPa, 134.2 MPa, and 4.0%, respectively. The phase transformation and dissolution mechanism during the homogenization process of 7075 aluminum alloy provides a scientific theoretical basis for improving the mechanical properties of the alloy.

Keywords

• 7075 aluminum alloy
• Homogenization
• Phase transformation
• Mechanical properties