On achieving superior strength for Al–Mg–Zn alloy adopting cold ECAP

Abstract

The current work aimed to investigate the effect of equal channel angular pressing (ECAP) on AA7075-T6 aluminum alloys, which were successfully processed at room temperature with six passes. Achieving sound microstructures and better mechanical properties due to cold ECAP were investigated. It was found that ultra-fine grains that owned an average grain size of about 103 nm were successfully achieved after six cold ECAP passes. Grain refinement, precipitation, and dislocation after ECAP have been evaluated. The results showed the η phases were fragmented with an increased density, and the η′ phases were significantly formed during the first ECAP pass. Consequent processing up to 6 passes presented that the GP zones have not been detected due to the transformation to η′, leading to the maximum η’ precipitate density of 7.1x1015 m-2 with the average size of 5.5 nm, while a very little η phases still detected after the redissolution. Besides, the microhardness of the adopted alloy was gradually increased. The yield strength was remarkably increased to 500 MPa with a significant improvement of 70.6% after a single pass. By increasing the passes number to 6, the strength of the ECAPed alloy was significantly improved to the maximum ultimate tensile strength of 647 MPa and yield strength of 605 MPa.