Study on the Formation of Globular Microstructure in 7075-Al alloy during Strain Induced Melt Activated (SIMA) process

Strain Induced Melt Activation (SIMA) process, is a semi-solid process to create globular grains in alloys. In this process, after applying a desired strain, the sample is heated up to semi-solid region and is hold for a desired time. In the present study, SIMA process was applied to form globular microstructure in 7075-Al alloy. The effects of strain value, strain temperature, semi-solid holding time and semi-solid holding temperature on the average grain size and shape factor were investigated. Optical and scanning electron microscopes were used to investigate the microstructure. The results revealed that, it is not possible to introduce a distinguished mechanism for generating the globular grains; while depending on the liquid fraction and strain value, there is a competition between recrystallization and internal melting of grains. Also, the results depicted that, in the SIMA process, the elongation would be increased with respect to T6 condition; while there is no considerable reducing in the strength.