AbstractEffects of magnetic fields up to 8 T on martensitic transformation and serration (discontinuous yielding) at 4 K have been investigated in Fe-37.4wt.%Ni alloy, Type 304L and Type 316LN stainless steels together with effects of applied elastic stress and plastic deformation of the transformation. Isothermal transformation was enhanced with increases in applied stress and magnetic fields. The amount of α′ martensite induced by plastic deformation in Type 304L and 316LN steels was increased by an 8 T magnetic field, and the increase was getting large with plastic strain. The amount of deformation-induced α′ martensite increased by the magnetic field was small in Fe-37.4wt.%Ni alloys. The applied magnetic field also suppressed the onset of serration in Type 304L and 316LN steels.