On the strain to the onset of serrated flow in a magnesium alloy

Acoustic emission and transverse strain measurements are used to show that small strain bands appear superimposed onto the homogeneous deformation from the onset of gross plastic deformation. The strain carried by the bands gradually increases until they completely suppress the uniform deformation, at strains between 1.5% and 5%, depending on the strain rate. When this happens, macroscopic serrations are detected in the stress–strain curve. The results are discussed in terms of a current non-diffusional theory for the Portevin–Le Chatelier effect.