As-Quenched Microstructures of Rapidly Solidified Fe-25 Wt % Ni

摘要

Specimens of rapidly solidified Fe-25 wt % Ni have been obtained by two-piston splat-quenching. The as-quenched microstructures varies from fully austenitic to almost completely martensitic. The microstructures have been studied by x-ray diffraction, scanning and transmission electron microscopy and x-ray microanalysis. The fully austenitic specimens reveal a fine grain size (1 to 5 mu m) with a high dislocation density of approx. 10 exp 11 dislocation lines cm exp -2 . There is evidence for the existence of sub-grain boundaries in some of the grains. In addition, two different martensitic microstructures are observed. In the specimens which have partially transformed to martensite during quenching, the structure is lath martensite with fine internal twins present in some laths. However, in austenitic specimens which have been transformed by cooling in liquid nitrogen, the microstructure is lenticular plate martensite with the characteristic mid-rib. The different structures found in rapidly solidified Fe-25 wt % Ni are discussed. (ERA citation 07:004709)