Identifying　the　defects　process　in　concurrent　recrystallization　and　precipitation　during　aging　a　supersaturated　solid　solution　is　essential　for　understanding　their　interaction　mechanisms　and　for　manipulating　the　microstructure,　but　was　rarely　done　at　the　atomic　scale.　Herein,　the　concurrent　recrystallization　and　precipitation　in　the　supersaturated　hexagonal　Sm(Co,　Fe,　Cu,　Zr)7.5　alloys　were　studied　through　detailed　transmission　electron　microscopy　investigations,　where　the　recrystallization,　growth　of　recrystallized　subgrains　(cells)　and　precipitates　stem　from　the　gradual　formation　and　dissociation　of　defects,　including　basal　stacking　faults　(SFs),　vacancies　and　excess　interstitial　atoms.　The　diffusion-controlled　glides　of　-type　partial　dislocations　associated　with　the　SFs　not　only　transform　the　matrix　from　the　mixture　of　hexagonal　Sm(Co,　Fe,　Cu,　Zr)7　(1:7H)　and　Sm2(Co,　Fe,　Cu,　Zr)17　(2:17H)　to　Sm-depleted　rhombohedral　Sm2(Co,　Fe,　Cu,　Zr)17　(2:17R)　cells　but　also　provide　continuous　diffusion　channels　to　reduce　the　point　defects　to　form　the　Sm-enriched　hexagonal　Sm(Co,　Fe,　Cu,　Zr)5　(1:5H)　cell　boundary　precipitates　and　Zr-enriched　rhombohedral　(Sm,　Zr)(Co,　Fe,　Cu)3　(1:3R)　platelets.　It　indicates　a　diffusion-controlled　displacive　phase　transformation　mechanism,　characterized　by　the　composition-dependent　2:17R’　intermediate　phase　due　to　incomplete　basal　slip　and　incomplete　solute　partitioning.　The　growth　velocities　of　both　recrystallized　cells　and　precipitates　are　closely　related　to　the　defects　density,　being　faster　due　to　the　high　defects　density　at　early　stage,　and　being　slower　due　to　the　reduced　defects　density　at　later　stage.　A　basal　slip　model　is　proposed　to　explain　the　formation　and　dissociation　of　defects　along　with　the　stacking　period　change　and　the　simultaneous　formation　of　continuous　atomic　diffusion　channels.　These　new　findings　may　yield　a　deep　understanding　of　the　interaction　between　recrystallization　and　precipitation.　©　2020