Assessment of Retrogression and Re-aging Treatment on Microstructural and Mechanical Properties of AL-Zn-Mg-Cu P/M Alloy

In order to understand the importance of the retrogression and re-aging as a heat treatment for improving microstructural and mechanical properties of the Al-Zn-Mg-Cu powder metallurgy alloys, Al-Zn-Mg-Cu-Fe-Cr alloys were fabricated from the elemental powders. Green compacts are compressed under compaction pressure about 370 MPa. The sintering process carried out for the samples of aluminum alloys at temperature was 650 degrees C under argon atmosphere for two hours. The sintered compacts were subjected into homogenizing condition at 470 degrees C for 1.5 hours and then aged at 120 degrees C for 24 hours (T6 temper) after that it carried out the retrogressed at 180 degrees C for 30 min., and then re-aged at 120 degrees C for 24 hours (RRA). Observations microstructures were examined using optical, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction. Density and porosity content was conducted for the samples of alloys. The result showing that the highest Vickers hardness exhibited for an Al-Zn-Mg-Cu alloy after underwent the retrogression and reaging treatment. Increasing in hardness was because of the precipitation hardening through precipitate the (Mg Zn) and (Mg2Zn11) phases during matrix of aluminum-alloy.