简介：Themicro-characteristicsofthestreakymarksandthecorrespondingsubstratesurfaceofgalvannealed(GA)steelsheetshavebeeninvestigatedusingSEMandFIB.Thestreakymarkareaseemstohavemanycavities,similartocraters,whichscatterlightandmakethesurfaceappeardarkerwhencomparedwiththesurroundingnormalarea.Moreover,itisfoundthattheirregularityordifferenceinsteelgrainsizetendstoaffectthesurfacequalityoftheGAsteelsheets.Duringalloying,thediffusionspeedofZn-Feonthegrainboundaryisfasterthanthatatthecenterofthegrain,whichresultsintheselectiveformationofcrater-likemorphologyinthecoatingareawithlargersteelgrains.DuetothecleargrainboundaryofIFsteel,apparentstreakymarkswillbeformedonthecoatin,iftheIFsteelsurfaceconsistsofrainsofirreularsize.