Serrated yielding due to Portevin - Le Chatelier effect in commercial Al-Mg alloys

Abstract

Abstract The mechanical characteristics of plastic deformation of commercial Al-1Mg, Al-2Mg and Al-2.5Mg alloys whose tensile curves present serrated yielding due to the Portevin - Le Chatelier effect (PLC) have been investigated in some detail. In this experimental work, tests at room temperature were conducted on a hard tensile machine and measurements of the most important parameters of serrated yielding showed the influence of the Mg content in these alloys. We also show that the Mg content is the factor responsible for a more or less heterogeneous plastic strain. The tendency towards serrated flow was characterized by the critical strain for the onset of PLC instabilities as well as by the magnitude of the stress drops. The strain rate dependence on the critical strain presents, in the domain of the explored strain rates, various types of behaviour: “normal”, “inverse then normal” and “inverse” for Al-1Mg, Al-2Mg and Al-2.5Mg, respectively. The evolution of type of instabilities vs. critical strain, the influence of the Mg content on the magnitude of the stress drop and their dependence on the strain and strain rate were studied. The experimental results are compared and discussed with reference to the literature data of a variety of Al-Mg alloys.