Effects of silicon on the microstructure and mechanical properties of 20％ cold-worked 15-15Ti austenitic stainless steels are systemically investigated by uniaxial tensile tests,scanning and transmission electron microscope observations,and strength calculations.The results reveal that a large number of deformation twins are formed in the 20％ cold-worked steels with various silicon additions.The volume fraction of deformation twins and the density of dislocations increase with silicon content,while the twin thickness slightly decreases.A better strength-ductility combination is achieved by silicon addition,since the yield strength of the steel with 2％ silicon is 61 MPa higher than that of the steel with 1％ silicon,while their uniform elongations are almost both equal to 16％.The yield strength of the 15-15Ti stainless steels is predominantly contributed by the solid solution,dislocation and deformation twin strengthening effects,which can be enhanced by silicon addition.