Modification of microstructure and mechanical properties of Al–Zn–Mg/3 wt.% Al^sub 2^O^sub 3^ composite through semi-solid thermomechanical processing using variable loads

The microstructure and mechanical properties of Al–Zn–Mg/3 wt.% Al2O3 composite were modified through a thermomechanical processing technique. The powders were cold pressed and solid state sintered for 90 min under argon atmosphere. Thermomechanical processing was then applied to the solid state sintered samples, which consisted of cold pressing followed by partial remelting for 30 min under argon atmosphere. Four different loads in the thermomechanical processing were used to investigate the effects of compressive loads on the microstructures and the mechanical properties. The results revealed modifications in the microstructure of the thermomechanically processed samples with the optimum combination of properties in the sample modified by applying the load of 250 MPa. Increasing the thermomechanical processing load decreased the amounts of porosity by about 7 %, decreased the average grain size to about 4 μm, enhanced the compressive yield strength to about 295 MPa, and increased the microhardness values from 250 HV to 600 HV. In addition, the energy absorption capacity increased by about three times.