Microstructural Evolution in AA7055 Aluminium Alloy Under Dynamic Shock Loading

The material investigated in this project is AA7055 Aluminium alloy at T7751 tempered condition. It was solution heat treated to obtain two additional temper conditions; T6 and T4. To produce the T4 temper, the as-received aluminium alloy was subjected to single-step heat treatment at 450oC for 1.5h and quenched in water. Other sets of as-received samples were subjected to two-step heat treatment which involves heat treating at 450oC allowed to homogenize for 1.5hrs and quenched in water. The as-quenched specimens were age-hardened for 8hours at 100oC and for 24hrs at 120oC. Upon impacting these alloys, maximum strength obtained for the T7751, T6, T4 tempered alloy are 822MPa, 748MPa and 640MPa respectively. Similarly, Compressive tests were carried out at a slow strain rate and the maximum strength obtained for T7751, T6, T4 are 1392MPa, 957MPa and 525MPa respectively. As a result of the dynamic impact test and slow strain rate deformation carried out on the aluminium alloys, adiabatic shear bands are seen mostly along the circumference of these alloys as detailed in the results section. This can be due to the high deformation resistance of these alloys, heat generated at the point of impact as well as dislocation of second phase particles distributed within the crystal structure are observed with the Scanning Electron Microscope