High-entropy　alloys　exhibit　some　interesting　mechanical　properties　including　an　excellent　resistance　against　softening　at　elevated　temperatures.　This　gives　high-entropy　alloys　(HEAs)　great　potential　as　new　structural　materials　for　high-temperature　applications.　In　a　previous　study　of　the　authors,　oxidation　behavior　of　Al0.6CrFeCoNi　and　Al0.6CrFeCoNiSi0.3　high-entropy　alloys　at　T　=　800　degrees　C,　900　degrees　C　and　1000　degrees　C　was　investigated.　Si-alloying　was　found　to　increase　the　oxidation　resistance　by　promoting　the　formation　of　a　continuous　Al2O3　layer,　avoiding　the　formation　of　AlN　at　T　=　800　degrees　C.　Obvious　phase　changes　were　identified　in　the　surface　areas　of　both　alloys　after　the　oxidation　experiments.　However,　the　effects　of　heat　treatment　and　Si-alloying　on　the　phase　transition　in　the　bulk　were　not　investigated　yet.　In　this　study,　Al0.6CrFeCoNi　and　Al0.6CrFeCoNiSi0.3　high-entropy　alloys　were　heat-treated　at　T　=　800　degrees　C　and　T　=　1000　degrees　C　to　investigate　the　effect　of　heat　treatment　on　microstructure,　phase　composition　and　mechanical　properties　of　both　alloys.　The　results　show　that　alloying　Al0.6CrFeCoNi　with　Si　caused　a　phase　transition　from　dual　phases　consisting　of　BCC　and　FCC　to　a　single　BCC　phase　in　an　as-cast　condition.　Furthermore,　increased　hardness　for　as-cast　and　heat-treated　samples　compared　with　the　Al0.6CrFeCoNi　alloy　was　observed.　In　addition,　the　heat　treatment　facilitated　the　phase　transition　and　the　precipitation　of　the　intermetallic　phase,　which　resulted　in　the　change　of　the　mechanical　properties　of　the　alloys.