Fe-Cu　and　Fe-Cu-Ni-Al　alloys　were　aged　at　500　degrees　C　for　different　time　after　solution　treatment　at　900　degrees　C　for　2　h.　The　influence　of　co-addition　of　Ni　and　Al　on　the　microstructure　evolution　of　Cu-rich　phase　was　studied　using　atom　probe　tomography　(APT).　APT　results　showed　that　the　addition　of　Ni　and　Al　effectively　increased　the　number　density　of　Cu-rich　particles　and　reduced　their　sizes　with　a　narrow　size　distribution.　In　the　peak　hardness　condition,　the　precipitates　in　the　Fe-Cu-Ni-Al　alloy　exhibited　a　core-shell　structure　with　the　Cu-rich　phase　in　the　core　and　NiAl　phase　in　the　outer　shell,　leading　to　a　dramatic　improvement　of　peak　hardness　and　strength.　The　NiAI　shell　of　the　precipitates　impeded　the　growth　and　coarsening　of　the　Cu-rich　phase　by　decreasing　the　interfacial　energy　and　the　diffusion　rate　of　Cu,　Ni　and　Al　atoms　in　the　shell.　After　further　ageing,　the　core-shell　structure　of　the　precipitates　decomposed,　forming　separate　Cu-rich　phase　and　NiAI　phase.