  Strengthening in age-hardenable alloys is mainly achieved through nano-scale
precipitates whose formation paths from the atomic-scale, solute-enriched
entities are rarely analyzed and understood in a directly-verifiable way. Here,
we discover a pathway for the earliest-stage precipitation in Al-Mg-Si alloys:
solute clustering leading to three successive variants of FCC clusters,
followed by the formation of non-FCC $GP$-$zones$. The clusters, which
originally assume a spherical morphology ($C1$), evolve into elongated clusters
and orient themselves on $\{111\}_{Al}$ ($C2$) and subsequently on
$\{100\}_{Al}$ planes and $<$$100$$>_{Al}$ directions ($C3$). We also analyze
the association of quenched-in dislocations with clustering phenomena. The
results of this work can open a new frontier in advancing
alloy-process-property design for commercially-important age-hardenable Al
alloys.
