Heat treatment of 7075 aluminum alloy by rheo squeeze casting

The main functions and purposes of alloy heat treatment are as follows: one is to improve the process performance of the formed parts and ensure the smooth progress of the subsequent processes; the other is to improve the performance of the parts and give full play to the potential of the materials. In order to obtain high mechanical properties, it is necessary to adopt appropriate heat treatment process to effectively improve the comprehensive mechanical properties of the formed parts. The heat treatable high strength aluminum alloy 7075 generally adopts solution treatment process, that is, heating to the temperature at which the second phase dissolves into the solid solution to the maximum extent, holding for a certain time, and then cooling rapidly to obtain supersaturated solid solution. After solution, the alloy can be strengthened significantly by aging treatment, so that the dissolved second phase precipitates in the form of dispersion distribution.

In the process of rheo squeeze casting, the alloy melt is subjected to mechanical static pressure, which makes the semi molten metal produce viscous flow, solidification and plastic deformation. A small amount of recovery and recrystallization occurs in the matrix, and a large number of dislocations and substructures are also formed. Therefore, exploring the heat treatment process suitable for rheo squeeze casting will effectively improve the properties of the formed parts. Combined with the characteristics of new rheo squeeze casting process of aluminum alloy, based on the experiments, the heat treatment process of 7075 aluminum alloy rheo squeeze casting part was optimized by discussing the changes of microstructure and mechanical properties parameters under different heat treatment systems, and the strengthening mechanism and tensile fracture mechanism were revealed.