Abstract

QUINTERO SAYAGO, Omar. Características microestructurales de una aleación comercial de hierro nodular. Rev. LatinAm. Metal. Mater. [online]. 2007, vol.27, n.1, pp.29-40. ISSN 0255-6952.

Nodular iron microstructural features at 100x and 500x, in the central zone of one specimen in as-cast condition, are discussed. Smoothed experimental data from its thermal analysis gave a cooling rate of 8.66 ºC/s. The liquid commercial alloy is regared as a Fe-C-Si ternary system alloy with Carbon Saturation Index, S_C = 1.04 (%CE = 4.42). External surface spheroidal graphite morphologies evidences are evaluated by the use of theoretical solidification fundamentals. Those graphite spheroids mainly show surface irregularities, protruded nodules, and also nodular-lamellar hybrids. The probable causes for that diversity of spheroidal microstructure are associated to process parameters related to liquid metal constitution of the alloy. Probable origin of such morphological features in as-cast condition is related to liquid metal constitution process parameters. Evaluation of thermodynamically metastable eutectic when is seen at 500x is performed in similar fashion as previously discussed. This transformed ledeburitic microstructure is predicted through the use of the designed computer modeling program called “ps3”. The transition stable to metastable eutectic reactions is discussed when increase of chemical potential is related to solid-liquid interface as consequence of surface energy alterations leading to the creation of changes in silicon segregation patterns inside the eutectic austenite.

Keywords : Nodular iron; Microstructure; Nodular morphologies; Transformed ledeburite.