Three　experimental　fully　austenitic　high-carbon　twinning-induced　plasticity　(TWIP)　steel　grades　were　produced　and　the　stacking　fault　energy　(SFE)　was　investigated　based　on　the　thermodynamic　modeling　approach.　The　SFE　of　Fe-20Mn-xCu-1,3C　(x　=　0,　1.5　and　3.0)　steels　varied　from　24.36　to　28.74　mJ　m(-2)　at　room　temperature.　In　order　to　study　the　correlation　between　the　SFE　and　the　mechanical　behavior　of　TWIP　steels,　tensile　tests　were　performed　at　room　temperature　and　the　deformed　microstructures　were　examined　at　different　strain　levels　by　transmission　electron　microscopy.　The　Cu　additions　resulted　in　a　remarkable　increase　in　total　elongation　without　a　slight　loss　of　tensile　strength.　In　addition,　the　critical　strain　for　serration　start　on　the　tensile　stress-strain　curves　(i.e.　required　strain　to　generate　mechanical　twinning)　was　found　to　increase　with　increasing　Cu　content.　Transmission　electron　microscope　(TEM)　observations　also　indicated　that　the　occurrence　of　mechanical　twinning　was　suppressed　by　increasing　the　Cu　addition.　The　strain　hardening　mechanism　and　the　superior　ductility　in　deformation　are　dominated　by　the　interaction　of　twins　and　dislocations.　The　mechanical　behavior　of　TWIP　steels　is　related　to　the　Cu　addition,　the　SFE,　the　interaction　of　twins　and　dislocations.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.