Microstructure and mechanical properties of Al–4·4 wt-%Mg alloy (AA5182) after equal channel angular pressing

Abstract

Equal channel angular pressing (ECAP) has been used to process an Al–4·4 wt-%Mg alloy (AA5182) at room temperature (RT), 200°C and 400°C. The evolution of microstructure and mechanical properties after ECAP has been studied by metallographic observation, EBSD analysis and compression testing. The results show that ECAP at room temperature yields high strength but poor ductility. Severe shear bands and a substructure consisting mainly of low angle boundaries have been observed. After 2–3 ECAP passes severe macrocracks appear. During ECAP at 400°C, discontinuous recrystallisation occurs and the fraction of recrystallised grains tends to increase with strain. The compressive strength (at RT) after ECAP at 400°C is low and remains constant with increasing number of ECA pressings. During ECAP at 200°C there is no evidence of discontinuous recrystallisation. The microstructure consists of a cellular structure with a mixture of low and high angle boundaries, which produces a good combination of strength and work hardening.