Investigation on creep mechanical properties and the relationship between creep cavities and deformation activation energy in 6082-T6 aluminum alloy joints welded by ring-spot laser

The 6082-T6 aluminum alloy welded joints were solution-treated at 480 °C and underwent tensile creep tests at 180 °C, 260 °C, and 450 °C. Results showed that the creep strain index n was significantly influenced by temperature and stress, with temperature having a greater impact. Higher temperatures shifted the creep mechanism toward dislocation creep , and at 450 °C, dynamic recrystallization enhanced creep mechanical properties, leading to a smaller strain index. Creep simulations revealed that void nucleation was linked to stress concentration zones, causing fracture in these regions, while elevated temperature and stress promoted void growth . Creep deformation induced grain boundary sliding , resulting in grain fragmentation and equiaxed structures. These structures facilitated the formation of precipitates and Al–Si–O compounds, increasing stress concentration and promoting void and crack growth.Increasing the temperature from 180 °C to 260 °C decreased deformation activation energy and creep resistance, whereas further increasing it to 450 °C had the opposite effect. Within a certain range, increased stress and temperature reduced deformation activation energy , promoting deformation and void growth , which in turn lowered the material's deformation activation energy. SEM and EBSD analyses showed that voids grew at grain boundaries with higher dislocation density . Prolonged aging time promoted void and dislocation aggregation, but dislocation motion was not the primary cause of creep failure. At 180 °C, the {110}<001> Goss texture dominated, while at 260 °C, the {110}<112> brass and unstable {112}<111> copper textures were prevalent. At 450 °C, other textures dominated and transitioned to copper textures, confirming temperature-dependent creep properties.In welded samples, void nucleation and diffusion activation energy were lower than the interfacial energy of plastic-growing voids, with grain boundary short-circuit diffusion as the primary diffusion pathway. Higher dislocation density at pores facilitated their aggregation at large-angle grain boundaries, aggravating grain boundary sliding and lattice diffusion . Internal pore surfaces likely drove grain boundary sliding and lattice diffusion, leading to sample failure at lower energy inputs . Creep life predictions under different experimental parameters closely matched experimental results.Based on the results, the optimal creep aging temperature for 6082-T6 aluminum alloy welded joints under loads within the yield strength range is 180 °C. This study offers theoretical guidance for improving the creep mechanical properties of 6082-T6 aluminum alloy welded joints.