Comparison of microstructures and mechanical properties of Al 7075 alloy obtained from conventional modified SIMA processes

In this study, the microstructures and mechanical properties of Al 7075 alloy obtained from conventional and modified SIMA have been investigated. In fact, the appropriate microstructure for the semi-solid forming is the non-dendritic microstructure with enough degree of spheroidity. In this research, a type of modified SIMA was used to make a comparison with the conventional SIMA. An annealed strip of Al 7075 alloy after rolling was soaked in an electrical furnace at 590 °C for different periods and then was cooled to 500 °C and quenched in cold water. After that, the mentioned procedure was repeated without rolling. The results showed noticeable improvement in the microstructure and the mechanical properties of the alloy processed by the modified SIMA. Not only was the globular structure finer and more homogenous but also, a more homogenous distribution of the secondary phase particles in a non-continuous manner was obtained at the grain boundaries and the eutectic structure was removed. These led to the improved mechanical properties such as ultimate tensile strength from 371 MPa to 442 MPa, elongation from 4.2 % to 13.1 %. In addition, although the maximum microhardness at grain boundaries decreased, the microhardness level within the grains improved and formability enhanced severely.