Effects of nanosized precipitates on the Portevin-Le Chatelier behavior: Model prediction and experimental verification

The influence of homogenously-distributed nanosized Al3(Sc, Zr) precipitates on the Portevin-Le Chatelier (PLC) behavior in a model AlMgScZr alloy was investigated by experimental characterization and theoretical modeling. A remarkable advantage of the selected alloy is that the solute Mg concentration remains unchanged during the precipitation of Al3(Sc, Zr) nanoparticles, which effectively rules out the influence of solute concentration change on PLC. Transmission electron microscopy (TEM) and small angle neutron scattering (SANS) were used for quantitative characterization of precipitates and evaluation of key modeling parameters. By comparing the results for AlMg (without precipitates) and AlMgScZr (with precipitates) the effects of precipitates on the PLC phenomenon were clarified. It was found that the precipitates decrease the critical strain for the occurrence of PLC. Further, by evaluating dislocation densities of both alloys via synchrotron X-ray diffraction (XRD), the influence of precipitates on PLC was clarified by revealing the different roles of solute atoms and precipitates played in the dislocation-dislocation interaction. A model was proposed to account for these phenomena.