The effect of precipitation on the Portevin-Le Chatelier effect in an Al–Zn–Mg–Cu alloy

The effect of ageing times and temperatures up to 200°C on the characteristics of serrated flow in an Al–Zn–Mg–Cu alloy was investigated. Tests at room temperature were conducted on a hard tensile machine. Experimental measurements of the serrated yielding show the important influence of precipitation. In particular, Guinier–Preston (GP) zones reduce the tendency to serrated flow and increase the onset strain of serrations, εc. Precipitates formed at high ageing temperatures favour the occurrence of serrated flow. However, the εc values remain higher than those observed for materials aged at very low temperature. The influence of precipitation of the magnitude of the stress drop has also been examined.