Influence of Intermetallics and Precipitates on the Fatigue Crack: Nucleation And Propagation in Aluminum Alloys 6005-T6, 6063-T6 and 6351-T6

Due to their favorable properties, among them the excellent strength-to-weight ratio, aluminum alloys are applied in transport vehicles, like trucks and buses. With respect to their mechanical behavior, fatigue is a process that alters the life of a structural component producing local stresses and floating strains and consequently giving rise to crack nucleation and the fracture of the material. In this work it is shown the influence of microstructure and intermetallic particles in aluminum alloy AA6005-T6, AA6063-T6 and AA6351-T6 that were tested for tension and fatigue. The microconstituents and the crack path on the fracture surfaces were analyzed by optical microscopy and scanning electron microscopy (SEM). The variation of the geometry of the precipitated particles of Mg₂Si, intermetallics (Fe,Mn)₃SiAl₁₂ and irregular distribution of particles in the matrix of the alloys were observed. The test results, together with the fractographic analyses, allowed determining the differences in the fatigue behavior of the studied alloys.