Effect of heat treatment on mechanical properties and energy absorption capacity of 7003 aluminum alloy

Abstract

The effects of heat treatment conditions on the mechanical properties and energy absorption capacity of 7003 (Al-6Zn-0.6Mg) aluminum alloy were studied. The extruded material was heat treated at various temperatures to prepare annealed or aged specimens. Tensile tests, hardness measurements, electron backscatter diffraction characterizations, and differential scanning calorimeter analyses were carried out to investigate the mechanical properties and microstructures of the as-extruded or heat treated specimens. Axial compression tests of circular tube samples were also performed to characterize their energy absorption behavior. Specific energy absorption was calculated by measuring the absorbed energy per unit weight of the tube specimen. The peak reaction force was defined as the maximum force applied during the compression test. The as-extruded material with high strength and low elongation exhibited fracture failure during the axial compression test. After a low temperature annealing at 200 or 250 oC, the material had low strength and low energy absorption capacity. In contrast, the high temperature (300 to 400 oC) heat treatment resulted in an increase in strength and enhancement of energy absorption capacity. The aging treatment effectively increased the strength and the energy absorption capacity. After artificial aging, fine and uniform precipitates were formed. The artificially aged specimens showed the highest yield strength and therefore exhibited the highest energy absorption capacity among the heat treated specimens. Specific energy absorption and peak reaction force were linearly proportional to the flow stress of the material.