High temperature mechanical properties and microstructure of die forged Al-5.87Zn-2.07Mg-2.42Cu alloy
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Materials Science and Engineering, Ministry of Education, Changsha 410083, China;
3. Centre for Clean Environment and Energy, Griffith University, Gold Coast, QLD 4222, Australia)
2. Key Laboratory of Nonferrous Materials Science and Engineering, Ministry of Education, Changsha 410083, China;
3. Centre for Clean Environment and Energy, Griffith University, Gold Coast, QLD 4222, Australia)
Abstract: The high temperature mechanical properties (250 °C) and microstructure of a die-forged Al-5.87Zn- 2.07Mg-2.42Cu alloy after T6 heat treatment were investigated. High temperature tensile tests show that as the temperature increases from room temperature to 250 °C, the ultimate tensile strength of the alloy decreases from 638 to 304 MPa, and the elongation rises from 13.6% to 20.4%. Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) were applied for microstructure characterization, which indicates that the increase of tensile temperature can lead to the coarsening of precipitates, drop of dislocation density, and increase of dynamic recovery. After tensile testing at 250 °C, a sub-grain structure composed of a high fraction of small-angle grain boundary is formed.
Key words: Al-Zn-Mg-Cu alloy; dynamic recovery; high temperature mechanical properties; microstructure