Microstructure of as‐extruded 7136 aluminum alloy and its evolution during solution treatment

Abstract With the aid of scanning electron microscopy (SEM), energy‐dispersive spectroscopy (EDS), X‐ray diffraction (XRD), differential scanning calorimetry (DSC) analysis and electron backscatter diffraction (EBSD), the microstructure of the alloy in as‐extruded state and various solution‐treated states was investigated. The results indicate that second phase of the as‐extruded 7136 aluminum alloy mainly consists of Mg(Zn, Cu, Al) ₂ and Fe‐rich phases. The Mg(Zn, Cu, Al) ₂ phase directly dissolves into the matrix during solution treatment with various solution temperatures. After solution treated at 475 °C for 1 h, Mg(Zn, Cu, Al) ₂ phases are dissolved into the matrix, while Fe‐rich phases still exist. Fe‐rich phases could not dissolve into the matrix by prolonging solution time. The mechanical property test and EBSD observation show that two‐stage solution treatment makes no significant improvement in mechanical properties and recrystallization of the alloy. The optimized solution treatment parameter is chosen as 475 °C/1 h.