Effects of pre-deformation on microstructure and tensile properties of Al-Zn-Mg-Cu alloy produced by modified strain induced melt activation

The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used by hot working at 300 °C. After pre-deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures (500, 550 and 590 °C) for varying time (10, 20 and 40 min). It was observed that strain induced melt activation has caused the globular morphology of α(Al) grains. Microstructural study was carried out on the alloy by using optical microscope and scanning electron microscope in both unrefined and B-refined conditions. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 550 °C and 10 min, respectively. After the T6 heat treatment, the average tensile strengths increased from 278 to 585 MPa and 252 to 560 MPa for samples refined with 3.75% Al-8B before and after SIMA process, respectively. The ultimate strength of SIMA specimens is lower than that of B-refined specimens.