SERRATED FLOW IN AL-5 WT PERCENT-MG ALLOY

Type B serrations in polycrystalline Al-5 wt.% Mg alloy at 296 K have been examined by a repeated process of strain aging and Lüders band propagation. The magnitude Δσ of the stress drop increases with strain and is proportional to (Dt) 2 3. This is in agreement with Cottrell's model of strain aging assisted by the enhanced diffusion of magnesium atoms through deformation-induced vacancies. Each stress drop Δσ results in a Lüders band motion with specimen extension Δl ∝(Δσ)1 - n, where n ≈ 0.3 is the effective stress exponent for Lüders strain in the stress relaxation mechanism proposed by Prewo et al. Higher ductility and work hardening may be explained through the larger travelling distance of Lüders bands associated with the longer aging time. © 1979.