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.