Thermal exposure of Al-Si-Cu-Mn-Fe alloys and its contribution to high temperature mechanical properties

The effect of Cu and Ti contents and thermal exposure on the elevated temperature mechanical properties of T6-treated Al-Si-Cu-Mn-Fe alloys was investigated via optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM), and elevated temperature tensile tests. The mechanical properties at elevated temperature increased with the increase in Ti and Cu contents. These results can be attributed to the increased amounts of precipitated particles. Thermal exposure at 300 °C for 10 h had a deleterious effect on the elevated temperature tensile properties due to the coarsening of the strengthening precipitates. Further thermal exposure up to 100 h only resulted in a little reduction in the strength. After thermal exposure at elevated temperature of 300 °C, the 4Cu-0.5Ti demonstrated best mechanical properties and Quality Index (QI). The ultimate tensile strength (UTS) at elevated-temperature of 300 °C were 170 MPa, 92 MPa, and 88 MPa for 0.5 h, 10 h, and 100 h after thermal exposure, respectively, which are superior to those for the commercial aluminum alloys.