Influence of T6 heat Treatment on the Mechanical Properties of AA7075 and AA7020 alloys

Abstract

The AA7075 and AA7020 alloys were prepared using a vacuum melting furnace and a casting furnace. Mechanical properties of the alloy samples were investigated as-cast and under heat-treated conditions. To investigate the effect of heat treatment, numerous designed AA7075 and AA7020 samples were homogenized (solution process) in two steps (300 oC/12h+475 oC/12h) and then aged under different regimes. The mechanical properties of microhardness (HV), ultimate tensile strength (σUTS), tensile yield strength (σTYS), compressive yield strength (σCYS) and Young's modulus (E) were measured to investigate the effect of heat treatment on mechanical properties. Both alloy systems (AA7075 and AA7020) were compared both within themselves and with each other in terms of mechanical properties depending on how they were subjected to the heat treatment. Depending on the applied heat treatments, 7075 alloy exhibited superior mechanical properties compared to 7020 alloy. A good combination of high microhardness and reasonable tensile strength has been achieved for both alloy systems by sequential and appropriate heat treatment. While the peak sUTS value reached for the AA7075 alloy was 425 MPa (regime 3), it was determined as 320 MPa (regime 2) for the AA7020 alloy. After the aging process at 150 oC/24h (regime 2) applied proceeding the homogenization process, the peak HV and sCYS values for AA7020 alloy were achieved as 1235 MPa and 321.6 MPa, respectively.