Highsolid-solubilityCo15Cu35alloyshavebeenpreparedbymeltspinningandsubmittedtoisothermalandanisothermalannealingtoobtaingranularalloys.TheX-raydiffraction(XRD)patternsweremeasuredtoinvesugatethedecompositionofsupersaturatedsolidsolutioninducedbyannealing.Theatomicdiffusionandstructuralevolutionduringtheheattreatmentwereinvestigated.Inviewoftheproblemslimitingtheirappllcation.thehigh-fieldmagneazationcurvesweremeasured.Byafittothehigh-fieldmagnetizationcurves,thegranuiaralloysarefoundhardtobemagneticallysaturatedattheearlystageofnucleationandgrowth.Themagnetizationbehaviorwascorrelacedtotheannealed-inducedstructurealevolutionandalsotothemagnetoresistanceeffect.