ItisfundamentallyimportanttounderstandtheinfluenceofstrainonthedensityofdeformationtwinsinTWIPsteelbecausetwinningisitsdominantdeformationmechanism.ThedeformationbehaviorofaFe-30Mn-4Si-3Al-0.097CsteelhasbeeninvestigatedbyX-raydiffraction(XRD),electronbackscatterdiffraction(EBSD)andtransmissionelectronmicroscopy(TEM)techniques.Samplewithanaveragegrainsizeof10μmwasdeformedincold-rollingwithareductionof10%,20%,30%,40%,50%,60%and70%,respectively.Themechanicalpropertiesofthecold-rolledsampleswerefurtherinvestigatedbytensiletests.Theyieldstrength(σy)andultimate-tensile-strength(σUTS)oftheas-preparedsampleis480MPaand850MPa,respectively.However,undercoldrollingdeformation,thetensilestrengthobviouslyincreaseswithanincreaseinrollingreduction.Thesamplewitharollingreductionof10%exhibitsσyof610MPaandσUTSof-1000MPa.Theyieldstrengthandtensilestrengtharefurtherenhancedupto1320MPaand1378MPaforthespecimenwitharollingreductionof70%,regardlessofthepoorductilityof6.7%.ThedeformationmicrostructureswerestudiedbyEBSDandTEMobservations.Itisfoundthat,withincreasingrollingreduction,theaveragedistancebetweendeformationtwinsdecreasesgraduallywhilethedensityofdeformationtwins(thelengthoftwinboundaryinunitarea)exhibitamaximumvalueat40%cold-rolling+tension.Carefullystatisticsanalysisrevealsgrainorientationiscloselyrelatedtothedeformationtwinsandtheunderlyingmechanismgoverningthetwinningisdiscussed.
