An　Al0.5CoCrFeNiSi0.2　high-entropy　alloy　was　prepared　by　vacuum　arc　melting.　The　alloy　was　aged　from　700　to　1100　degrees　C.　The　effects　of　aging　on　the　phase　transformation　and　mechanical　performances　were　explored.　The　as-cast　alloy　showed　a　dendritic　(DR)　microstructure.　The　DR　region　was　an　Fe,Cr-rich　FCC　phase,　while　the　interdendritic　(ID)　region　was　a　spinodal　structure　composed　of　Fe,　Cr-rich　BCC　(A2)　and　Ni,Al-rich　BCC　(B2)　phases.　At　aging　temperatures　between　700　and　900　degrees　C,　the　Fe,Cr-rich　BCC　(A2)　phase　in　the　ID　region　transformed　into　sigma　and　Fe,Cr-rich　FCC　phases.　Meanwhile,　some　Ni,Al-rich　FCC　phase　particles　precipitated　from　the　DR　region.　During　aging　at　1100　degrees　C,　the　DR　microstructure　disappeared,　and　a　microstructure　composed　of　Fe,Cr-rich　FCC　and　Ni,Al-rich　BCC　(B2)　phases　both　possessing　a　lamellar　shape　was　developed.　The　alloy　exhibited　evident　hardening　and　lower　tensile　strain　when　the　aging　temperature　was　lower　than　1000　degrees　C,　which　was　mainly　attributed　to　the　generation　of　the　sigma　phase　in　the　ID　region.　However,　a　contrasting　behavior　was　observed　when　the　aging　temperature　was　higher　than　1000　degrees　C,　which　was　attributed　to　the　redissolution　of　the　sigma　phase　and　the　microstructure　coarsening.