Microstructural evolution and mechanical properties enhancement of AA5083 alloy processed by equal channel angular pressing

Abstract

AA5083 is a widely used 5xxx series aluminum alloy for structural applications because it combines moderate strength, formability, weldability, and corrosion resistance. As a non-heat-treatable alloy, further strengthening requires deformation-based approaches such as severe plastic deformation. This study investigates the effect of Equal-Channel Angular Pressing (ECAP) ram speed on AA5083-O using a single ECAP pass at room temperature through a 90° die. The single-pass design was selected to isolate the initial speed effect from cumulative strain-path effects associated with multiple passes. Four ram speeds were examined: 10, 50, 100, and 150 mm/min. Microstructural analysis showed that ECAP substantially refined the as-received grain structure from 75 ± 8 μm to a speed-dependent refined structure; the finest measured average grain size was 6.1 μm at 150 mm/min. Mechanical testing showed clear improvement in all ECAP-processed conditions. The average microhardness increased from 76.1 ± 1.2 HV in the as-received alloy to 86.6 ± 2.9, 87.8 ± 1.7, 88.4 ± 3.4, and 87.7 ± 1.2 HV at 10, 50, 100, and 150 mm/min, respectively. The maximum hardness was therefore obtained at 100 mm/min, corresponding to a 16.2% increase relative to the base material. The compressive yield strength and ultimate compressive strength increased with ram speed and reached 315 ± 5 N/mm² and 395 ± 8 N/mm², respectively, at 150 mm/min. The strengthening response is mainly attributed to grain refinement and strain hardening, while possible recovery or localized thermal softening at the highest speed is discussed cautiously because temperature and dislocation density were not directly measured.