On the strain rate dependence of the critical strain for plastic instabilities in Al-Mg alloys

The strain/strain rate range of plastic instability in Al-Mg alloys is analyzed within the dynamic strain aging interpretations of the Portevin-Le Chatelier effect. The analysis focuses on several phenomena occurring around the minimum of the critical strain for the onset of serrations vs. applied strain rate curve. The analysis of the strain rate dependence of the flow stress strain rate sensitivity in the neighborhood of this critical point allows explaining the extension of the stability region to larger strains in the inverse behavior range and the shift to larger strain rates of the critical point when the Mg content increases. [Display omitted]