Through ribbon cooling rates and related nanostructures in melt spun Fe/Ni base hyperquenched alloys

An evaluation of the cooling rates and of the speed of the solidification front through the ribbon thickness during the processing of melt spun Fe40Ni40B20 and Fe50Ni29Si12B9 glass forming alloys was carried out by an analytical approach. The characterisation of the ribbons was accomplished by means of light microscopy, X-ray diffraction and TEM examination. The observed structures are related to the computed cooling rates, which are different on the wheel and on the gas side of the ribbons. Heat treatments performed at different temperatures affected both the hardness on the wheel and gas side of the ribbons and the extent of the passive behaviour in potentiodynamic polarisation tests.