Elimination of stretcher strain marks in high-Mg Al-Mg alloys: deformation behavior and microstructural insights in H16 temper

The influence of the Mg content on deformation behavior and formation of stretcher strain marks (SSMs, also known as Portevin–Le Chatelier (PLC) bands) was systematically investigated in high-Mg Al-Mg alloys subjected to 60% cold rolling (H16 temper). An innovative Eco-Al casting process was employed to introduce Mg via an Al 2 Ca-containing Mg master alloy. Tensile testing coupled with Digital Image Correlation (DIC) analysis revealed a clear dependence of SSMs characteristics on Mg concentration. Specifically, the Al-6Mg alloy exhibited early initiation of SSMs; the Al-7.5Mg alloy showed a delayed onset with more localized deformation, whereas the Al-8.5Mg alloy demonstrated complete suppression of SSMs, resulting in uniform deformation, enhanced elongation, and increased strength. X-ray diffraction (XRD) analysis confirmed a progressive increase in dislocation density with increasing Mg content. Electron backscatter diffraction (EBSD) results revealed the synergistic effect of a higher fraction of high-angle grain boundaries (HAGBs), moderate texture intensity, and more uniform distributions of kernel average misorientation (KAM) and geometrically necessary dislocations (GNDs). Collectively, these microstructural features promote distributed plasticity and effectively delay or suppress strain localization. In particular, Al-8.5Mg alloy exhibited the most enhanced mechanical performance and superior surface integrity, highlighting its strong potential for high-performance automotive and aerospace applications. • Progressive Mg addition suppresses stretcher strain marks (SSMs) in cold-rolled Al–Mg alloys. • Al–8.5Mg alloy exhibits complete SSM elimination with improved strength and ductility. • Dislocation density increases with Mg content, as confirmed by XRD and EBSD analyses. • Texture moderation and higher HAGB fraction in Al–8.5Mg enable uniform deformation. • Integrated DIC, XRD, and EBSD analyses provide mechanistic insights into SSM suppression.