In the current research, the effect of severe plastic deformation on microstructure and mechanical properties of Al-7075 alloy focusing on toughness was investigated. For this purpose, the Al-7075 alloy was subjected to ECAP process up to 4 passes by route BC at room temperature. Microstructure and fracture surface of the specimens were analyzed by optical and electron microscopy and mechanical properties were studied by hardness, tensile and impact tests. Dynamic and static toughness of the alloy were measured from the area under the stress-strain curve and impact test, respectively. The experimental data revealed that after 4 passes of ECAP, the grain size decreased from 40 µm to about 600 nm, and the hardness and strength of the specimen increased about 2 times in comparison with initial material. Static and dynamic toughness decreased about 62% and 30% after the first pass of ECAP, respectively. While, by increasing the pass number, the static toughness increased and dynamic toughness remained approximately constant. The fracture surface of specimens revealed that the fracture of all specimens was ductile. ECAP process caused a considerable increase in strength of Al-7075 (more than 100 percent), whereas, the toughness declined slightly during ECAP process (about 30 and 5 percent in dynamic and static toughness, respectively). So, it can be concluded that one the most advantages of ECAP process in comparison with common forming process is the notable improvement of strength without considerable sacrifice of toughness.

Keywords: ECAP process, Al-7075 Alloy, Dynamic toughness, Static toughness, Fractography

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