Effect of secondary-phase particles on microstructures and creep properties of A2618 aluminum forged alloy

In this study, the effect of secondary-phase particles on microstructures and creep properties of A2618 aluminum forged and then T61-tempered alloy was investigated by creep test, tensile test, SEM (Scanning electron microscopy)-EBSD (Electron backscatter diffraction) measurement, and X-ray diffraction analysis. Two samples with differently distributed secondary-phase particles were prepared by permanent-mold casting (MC) and furnace cooling within graphite crucible (FC). Steady-state creep rate was smaller and creep rupture time was prolonged in MC sample with denser and finer secondary-phase particles, and grain boundary strengthening by the particles was found to be responsible for the improved creep properties of MC sample. The result of in-situ heating SEM-EBSD measurement suggested that more notable recrystallization through particle-stimulated nucleation occurs in MC sample, resulting in the refined recrystallized grains with a higher coverage ratio of secondary-phase particles along grain boundaries.