Type-B serrations were observed during room-temperature tensile deformation of Al-2.17 mass%Mg alloy with an average grain size of 12 µm. Digital image correlation was used to visualize Portevin-Le Chatelier (PLC) bands, and microstructural changes in these bands were observed by in-situ X-ray diffraction measurements using synchrotron radiation at SPring-8. The results indicated that the overall density of dislocations, including both mobile and pinned dislocations inside the PLC bands, increased substantially as the bands formed. This suggests that serration occurs due to an increase in the mobile dislocation density resulting from the formation of new dislocations from sources inside the PLC bands.

This Paper was Originally Published in Japanese in J. Japan Inst. Light Met. 73 (2023) 628–632.