Serrated flow and work hardening characteristics of Al-5356 alloy

Stress–strain characteristics of Al-5356 are studied. Stress oscillation (repetitive stress drop or serration) in stress–strain relations (jerky flow or the Portevin–Le Chatelier (PLC)) was observed at the temperature ranging from 303 to 373 K at strain rate (S.R.) of 1.5 × 10−3 s−1. A relation between the stress reload parameter ΔσR and the strain ɛ in the jerky flow was found to be in the form [ΔσR = A exp(ɛ/α)] with a growth constant α independent on grain diameter d and /or deformation temperature Tw. The effect of grain diameter d on the work-hardening parameters (WHP) yield stress σy, fracture stress σf, total strain ɛT, work-hardening coefficient χp(=dσ2/dɛ) and the strain-hardening exponent n(=d ln σ/d ln ɛ) of Al-5356 alloy were evaluated at the applied deformation temperature range. The grain diameter d and deformation temperature Tw significantly decreased the total strain ɛT, the yield stress σy and the fracture stress σf of the tested samples, while the strain-hardening exponent n changed slightly. The relationship between the yield stress σy of the alloy under investigation and temperature follows an Arrhenius law. The mean activation energy of the deformation process was found to be ∼87 kJ/mole, close to the activation energy of grain boundary diffusion in aluminum alloy.