Itiswellestablishedthatdipolarinteractionsincolloidalmagneticfluidsarethemechanismofthepatternformationsuchaschainsorcolumns.Wereportthefirstobservationofstructureformationinsteelsexposedtoamagneticfield.Amagneticfieldhigherthan2Tisfoundtoalignthemicrostructureofsteelsparalleltothefieldduringthetransformationfromtheparamagneticfccphasetotheferromagneticbccphaseandviceversa.Evidenceispresentedforthedipolarinteractionsbetweentheellipsoidalnucleiinthebackgroundofthematrixwithadifferentmagneticcharacter.Electronbackscatteringdiffractionhasrevealedthatthetransformingnucleiinamagneticfieldareatrandomintheircrystallographicorientation.r2002ElsevierScienceB.V.Allrightsreserved.