Research on the lack of alloying in the galvannealed coating of automotive sheet steel

Samplesofthecrosssectionmicrostructuresofgalvannealedsteelsheetsthatlackalloyingwereanalyzed.X-raydiffraction(XRD)testswerecarriedout.Thestudydiscoversthatthedeficitofalloyingwashigheronbothsidesofthesteelsheetwhencomparedtothecenterandthethicknessofthecoatingonthesideswasalsohigherthanthecenter.TheresultsoftheXRDtestsdemonstratethatthemicrostructureofthecoatingwithalackofalloyismainlycomposedofzinc,ζandδ.Theyalsoindicatethatthelackofalloyingismainlyduetoalowergalvannealingtemperatureandthickercoating.Itisshownbytheopticalmicrographsofcoatingthattheδphaseformsfirstinadiscontinuousmannerattheinterfaceandthenrapidlypushestowardsthecoatingandenlarges.